THE PHYSIOLOGY OF HEALTH

AND DISEASE.

CHAPTER THE FIRST.

INTRODUCTORY.-STRUCTURE AND FUNCTIONS OF THE STOMACH. OBVIOUS as are the distinctions between animals and plants, when we contemplate their higher groups, it is no easy thing to give a definition that will at once distinguish the one from the other throughout all organic nature. The aphorism of Linnæus, That minerals increase, vegetables increase and live, and animals increase, live, and feelwill not help us much in distinguishing animals from plants. What is meant by feeling? If we define it as a movement resulting from stimulus, then the sensitive plant, and sunflower, and a hundred other plants possess it. If we define it as a movement connected with a nervous system, then the sponges, many zoophytes, and other animals, possess it not; for we can find in them no nervous system.

Aristotle said that an animal differed from a plant in the possession of a mouth. Difficult as it may be to detect a mouth in some of the smaller organisms, it perhaps is the most available of all the definitions that have been given. It also indicates another fact, and that is, that an animal possesses a stomach. Plants have no stomach; they derive their nourishment from the air and soil in which they live, and are as animals turned inside out. (Fig. 1.)

other parts of the animal are, as it were, subservient.

Animals live without nerves, bloodvessels, and muscles; but none exist without a stomach. The materials of which all other organs in the body are composed, are first prepared and elaborated in the stomach; and Man, with his great apparatus of his existence, is dependent, in common with organs for fulfilling the various conditions of the minutest animalcule, on his stomach for the various functions he performs. It is through the medium of the stomach that the blood is produced, that the coarse forms of external matter are reduced and refined, so as to become fitted to form part of his material frame. Hence the stomach is one of the most important organs in the human body; and the functions it performs are of a primary value, in relation to the other functions of the system.

It must not, however, be supposed that the only distinction generally present between plants and animals is the possession of a stomach by the latter. This is a matter of structure; and when we come to funcperformance of certain functions in plants is tion, we see that, although the end of the the same as that of animals, the way in which the functions are performed is very different. The consideration of this difference between the means employed for the performance of functions in animals and plants, embraces a very interesting general relationship between these two kingdoms of nature. We find, in fact, that all the food that is taken into the stomach of the animal is elaborated in the system of the plant; that, although man and other animals partake of animal food, the substances which they thus take are derived from animals which feed upon plants. Not only do plants supply animals with food, but they are mainly fed by means of two substancescarbonic acid gas and ammonia, which are thrown off by animal bodies, and which, if they remained in the atmosphere, would render it impure, and unfit for the existence of animals. Nor is this all; for we find that during the use of their food, animals are constantly taking up oxygen gas from the atmosphere, which, if it was not replenished, would be speedily reduced, so that the air we breathe would not support life. Oxygen gas is constantly given off by plants, and thus the atmosphere is purified by new accessions of the element it is constantly losing during the respiration of animals. These observations will show how different are the functions perfermed by the animal and vegetable kingdoms, and at the same

time point out the dependence of the one kingdom on the other."

But to return to the stomach. In the lowest forms of animals this organ is very simple, as is seen in the class of animacules. Most of these animals seem to consist of a simple vesicle, the whole of which may be regarded as a stomach. In the inside of some of them several vesicles may be seen attached to a common tube: these vesicles have been regarded by their discoverer, Ehrenberg, as stomachs (Fig. 2); hence

stomach becomes much greater when we have mentioned to those belonging to the pass from the lower forms of animals we highest classes, such as the fishes, reptiles, birds, and mammalia. In examining into the minute structure of the stomach of the various forms of animals, we find remarkable adaptations to the kind of food of which the animal partakes, and the circumstances in which it is placed. Thus, as a rule, it is found that vegetable food is more difficult to digest than animal

Fig. 2.

[Vorticella citrina, an infusorial animalcule. a the mouth, b commencement of stomach, ce continuation of same, df pouches or prolongation of stomach.]

the term polygastric (many-stomached), which he has applied to them. Other observers, however, do not agree with Ehrenberg with regard to the nature of the vesicles in the interior of animacules, which he calls stomachs. One thing is certain, that amongst these creatures we have very simple forms of digestive apparatus. The freshwater hydra (Fig. 3) is another creature belonging to a class of animals (Polypifera), higher in their organization generally than the polygastric animalcules, which exhibit a very simple form of

stomach.

As the nervous and other systems of the animal become complicated, and we ascend in the animal scale, we find the stomach assuming a more definite form, and extended into an intestinal tube. In the simple forms of creatures we have spoken of, there is no distinction between the bag of the stomach, and the parietes of the animal forming its body; but when we ascend to the insects and shell-fish, we find it lying amongst a number of other organs. (Fig. 4.)

The complication of the structure of the

Fig. 3.

[Hydra viridis, a species of fresh-water polype. its Interior, bb tentacula, whereby it lays hold of -a the body containing a cavity (the stomach) in its prey.]

food; and throughout the whole animal kingdom, the size of the stomach, and the length of the intestinal tube, are greater in herb-eating than flesh-eating animals. In creatures also that ruminate, a remarkable complication of the stomach alone is found, in order to carry on that function (Fig 5).

In ruminating animals the food, roughly cut by the teeth, is received into one cavity of the stomach, and passed into a second, in which it becomes soaked, and is thence passed into the mouth; where, being placed between the teeth of the animal, it is subjected to a second process of mastication, which is called rumination. It is then swallowed a second time, and passes into two other cavities in the compound stomach, before it is in a fit state to be taken up into the system. The stomach of carnivorous animals is a remarkable contrast to that of the ruminants. In these creatures, as the lion, tiger, &c., it assumes the simplest form, the flesh they eat requiring little preparation for digestion. The stomach of man stands truly between these two classes-of herb-eating animals on the one hand, and flesh-eating on the other-thus indicating that he is intended for a mixed

organs attain their fullest development in the cephalopodous class, which includes the nautilus, argonaut, and cuttle-fish; here the tentacles are powerful and complicated organs, enabling their possessors to secure for food animals higher in organization than themselves. In the articulate animals, as the worms, insects, crabs, lobsters, and spiders, the hard external skeleton of the animal assumes various forms, to facilitate the taking of prey, and the conveying it to the mouth. The segments of the skeleton, forming the jaws, are furnished with additional organs for this purpose; and, in the nippers of the crabs and lobsters, we have a remarkable example of the adaptation of the fore-feet to the need of the animal for holding powerful prey.

From the Invertebrate we pass to the Vertebrate animals: and here we meet with the Fish using its mouth for this purpose. The mouth of the fish is supplied with teeth, but they are not used in the same way as the teeth of man, but as organs of prehension. It is by means of the teeth that the fish holds his prey when it is seized, previous to swallowing. In the carnivorous reptiles we find the same arrangcment; and the dreaded teeth of the Crocodile are not organs of mastication, but of prehension. In the Birds, the tooth of the fish and the crocodile is modified into a beak or bill, the object of which is to pick up food, previous to its being conveyed into the gizzard. Amongst some of the birds, especially the tribe to which the parrot belongs, the foot and claws are used as assistants to the bill in performing this office. In the Mammalia we find very curious adaptations of particular structures to this function. In most instances the teeth and jaws are the only instruments. In the carnivora, however, the legs and paws of both fore and hind-feet are used in seizing and securing prey. In the monkies we find the nearest approach to the human hand, wanting however, in that wonderful completeness which is given by the opposable thnmb: they use also the fore and hindfeet alike for the purpose of seizing and conveying food to their mouth. In some animals, an elongation of the upper lip serves the purposes of prehension, as in the giraffe, and in many of the deer tribe. An elongation of the nose is frequently likewise used for prehension amongst the pachyderms; and we cannot fail to observe that the tapir is a transition from the hog to the elephant.

(To be continued.)

A SCENE AT VENICE. ON emerging from these dark passages, we observed, floating silently down the grand canal, a barge over which a hundred coloured lamps were suspended. We had not time to express our surprise before its occupants began to sing.

In another moment we were in a gondola, and followed the bright, mysterious object before us. The beautiful chorus ceased, and all was silent again. On our nearer approach, we saw, gliding on each side of the singers, a royal gondola, ornamented with blue velvet drapery surmounted by a gilded crown. Each boat was rowed by four gondoliers. In one sat the two Archdukes of Austria, in another the two Duchesses. Two or three gondolas with attendants were behind. A few followed, like ourselves, from curiosity. No light appeared from any window, no face looked from the fair marble balconies, no voice cried God bless them, as the small procession slowly glided onwards. How different was this to the hearty welcome given to British princes when visiting the great towns of our free country. The royal party now stop under the arch of the Rialto, and hear another song. A few persons gather on the quay to listen, and give a faint applause. Sometimes but one solitary individual claps his hands. The sound echoes dismally through the silent streets. A closely covered gondola occasionally darts from some hidden water-lane, skims swiftly past us, and is lost again in the dark night. The bright lamps and beautiful singing do not tempt the proud Venetian to look from his gloomy canopy. The songs are spirited, partly dramatic. In one performance two men tie handkerchiefs over their heads, and imitate the conversation of very loquacious old women. After remaining some minutes under the Rialto, the gondoliers begin to ply their oars, and quietly the whole company float up the canal, under the shadow now of one palace, now of another. Very gently we all glide along. The chorus, breaking forth at intervals into fresh harmonies, dies suddenly away, and then we hear nothing but the tiny ripple which the water always sings to the boat.

THE RESIDENCE OF BENJAMIN FRANK

LIN, CRAVEN STREET, STRAND. There are certain buildings in London which, although they have neither any peculiar beauty of architecture or picturesque appearance, have a considerable amount of interest to every intelligent person. We

drink, notwithstanding he did not refuse to become responsible for the ale scores of his fellow-workmen at the public house next the archway, which adjoins the premises. During a portion of the time he worked here, Franklin, thinking that the exercise would be beneficial, left his work at com

have still existing in Westminster, the iden- | avoiding every description of stimulating tical house which was for some time occupied by Milton, when Latin secretary to Oliver Cromwell; this was also occupied by Hazlitt, who placed on its wall a tablet to associate it with "The Prince of Poets." Its garden, in which is a tree said to have been planted by Milton, afterwards came into the possession of Jeremy Bentham, of famous memory. This object, so far as its general appearance is concerned, might be passed by without notice; but who, knowing its associations, could fail to look upon it without feelings of intense interest. The house in which Chatterton died his sad and untimely death, in Brook-street, Holborn, has but little external attraction, and yet, who that has rightly estimated this bright genius, can pass this plain dwelling, without many thoughts which are difficult to describe. The dwelling-places in which Sir Isaac Newton and other worthies spent a large portion of their useful lives, are still in existence, and few of them have a greater interest than that now engraved, which is connected with a brilliant portion of the career of the famed American philosopher.

FRANKLIN'S RESIDENCE.

posing, and took to the hand-press. A corner on the first floor of Messrs. Cox and Wyman's printing-house, is pointed out by some of the old men there employed, as the spot on which Franklin pursued his labours; and it is related that when he afterwards visited England, with a great reputation which extended throughout Europe, he called at this office, and addressing himself to a pressman here at work, said, "My friend, it is now some years since I worked at that press; let us, notwithstanding, take a pot together." While working at Messrs. Cox's, Franklin lodged with a poor widow, in the narrow street which leads from the archway on the west side of Lincoln's-Inn Fields. Although diligentenquiry has been made, we have failed to find

any distinct proof which of the houses

When Benjamin Franklin first visited | it was in which he lodged. Respecting the London, he went to work as a journeyman, subject of the engraving, there is no unin a printing-office in the neighbourhood of certainty; here, when he came in an St. John's Square, Clerkenwell; we have, honourable position from his native land, however, failed to trace anything in con- which he had by his energy and ability, nection with him in that place. He after- been such an important means of liberating, wards found employment in the printing he transacted important business and received establishment of the Messrs. Cox, (now Cox visits from the most distinguished and reand Wyman) in Great Queen Street, Lin-markable personages of the time. It would coln's-Inn Fields; here he pursued for be a useful plan to mark houses such as about twelve months, a life of steady in- those referred to, with a brief record of the dustry, living on the most simple food, and associations connected with them.