seen of the cancer cells excepting here and there granular remnants of protoplasm (Fig. 52, d). Since a like degeneration affects the septa of the alveoli, the latter coalesce to form larger and larger spaces (Fig. 52, b), which give the tumour a distinctly alveolar structure even to the naked eye.

The stroma in many cancers is very rich in blood-vessels, or consists almost exclusively of such (teleangiectatic carcinoma). In these cases hæmorrhages of greater or less extent may take place into the parenchyma of the cancer, resulting in pigmentation (fungus hæmatodes).

5. (iv.) Papilloma.-Even with the naked eye the papilloma can be seen to be composed of excrescences varying in length and thickness. Each of these latter, again, consists of a simple or ramified papilla, formed after the type of the papillæ of the skin or mucous membrane as the case may be, or of the villi, and carrying a covering

FIG. 54.-VERRUCA DURA OF THE SKIN. x 95. (Alum cochineal.) a, Greatly elongated papillae; b, Papillæ not so much elongated; e, Rete Malpighii; d, Greatly thickened fissured stratum corneum.

of epithelium of variable thickness (Fig. 53 and Fig. 153). The connective tissue in these papillæ and villi is commonly much richer

in cells and blood-vessels than in those of the original tissue, and the layer of epithelium may also be considerably thicker, although in all its other characteristics it usually corresponds with that of the region in which the tumour is situated. Papillomata arise from the normal papilla of the skin and mucous membranes, and in their formation there occurs not only an enlargement of the latter but also a new formation of papillæ.

Cutaneous warts are papillomata with an abnormal degree of horny transformation of the epidermis, causing the latter to rise in a conical form above the enlarged or newly-developed papilla (Fig. 54). acuminate condyloma likewise belongs to the papillomata.

The

Those papillomata of mucous membranes which are constructed more after the type of the intestinal or synovial villi, as for example. the papillomata which occur on the mucous membrane of the urinary bladder, are also called villous tumours (Fig. 153).

6. (v.) Polypi.--These occur only upon mucous membranes, of which they form outgrowths or circumscribed elevations, containing as a rule elements similar to those in the particular mucous membrane itself, and hence always covered with an epithelial coat which usually corresponds to that of the parent tissue (Figs. 55 and 56, a).

x 285. (Hæmatoxylin and eosin.) a, Cylindrical epithelium consisting of several layers of cells; b, Round cells; e, Spindle-shaped cells; d, Stellate cells, with and without pigment; e, Injected blood-vessels.

The rest of the tissue of polypi shows a somewhat variable composition. It consists either of fibrous connective tissue with but

few cells (fibrous polypus), or of an oedematous connective tissue or mucous tissue (mucous polypus, Fig, 55), or lastly of a round-celled tissue (sarcomatous polypus). In many polypi there also occur more or less abundant glands (Fig. 56, b), which correspond in size and general character with those of the particular mucous membrane, but often exhibit cystic dilatations (cystic polypi).

FIG. 56.-GLANDULAR NASAL POLYPUS. x 110. (Alum cochineal.)

a, Stratified cylindrical epithelium of surface; b, Acini, some rather
dilated, with cubical epithelium; e, Ducts with stratified cylindrical
epithelium; d, Blood-vessels; e, Small-cell infiltration.

The degree of vascularity also varies, some polypi being poorly supplied with vessels, whilst others on the contrary are so vascular that they resemble a cavernous tumour, in which case hæmorrhages and pigmentation readily occur (Fig. 55). The surface of polypi is usually smooth, but occasionally shows shallow (Fig. 56) or deep depressions like those in a papilloma (papillary polypi).

Examination of Tumours. This may be carried out while the tumours are fresh, as well as after hardening. In the former case, either the juice of the parenchyma is examined, which can usually be obtained only from the cut surface of the carcinomata and of the highly cellular sarcomata by scraping; or else torn up preparations, or lastly, sections made with the freezing microtome are used.

The juice of the parenchyma may be stained before transferring it to the slide by agitating it with picro-carmine or alum cochineal in a watchglass, and then after some minutes with a like quantity of glycerin, and taking a drop from this to examine. Needled preparations may be subjected to a similar process. In order to isolate the smooth muscular fibres in myomata, small pieces are laid in a 33 per cent. caustic potash or soda solution, or in 20 per cent. nitric

EXAMINATION OF TUMOURS

111

acid (p. 6); and to isolate the non-medullated nerve-fibres of neuromata, in half per cent. acetic acid.

For the specific reactions of fat, mucin, and deposits of lime and pigment, the methods given on pp. 53, 55 and 60-62 may be resorted to.

Hardening of tumours is done in alcohol when it is desired to attain that end rapidly or to preserve any calcareous deposits that may be present. If, however, the red blood-corpuscles are to be retained, hardening should be done first in Müller's fluid and then in alcohol, a proceeding which is also to be recommended for very soft or mucinous tumours, and in general in the majority of cases. For staining, carmine solutions and the double stains (pp. 18-21) in general are used, the latter especially with preparations hardened in Müller's fluid. In addition to the above the following should also be noted for individual varieties of new-formations:

In examining and staining chondromata and osteomata, the methods given in Part III., Chapter X., may be employed.

For staining the smooth muscle fibres in myomata, hæmatoxylin and eosin, and picro-carmine or picro-lithium-carmine, are to be recommended.

To stain the medullated nerve fibres in neuromata, the methods described in Part III., Chapter IX., are to be referred to.

Hæmatangiomata, after hardening in Müller's fluid, are stained with hematoxylin and eosin.

Both single and double stains are suitable for sarcomata and carcinomata. For the purpose of distinguishing alveolar sarcoma from carcinoma, as well as generally for the demonstration of the stroma, sections are to be carefully brushed with a hair pencil or shaken up in water (p. 17).

The majority of the benign tumours, such as fibroma, lipoma, chondroma, osteoma, and angioma, can commonly be determined even from their macroscopic appearance; but in the case of the other tumours also, an important indication for diagnosis is afforded by certain gross anatomical or clinical characteristics. Thus rapidity of growth, indefiniteness of boundary, great softness, ulceration, and the formation of metastases, point to sarcoma and carcinoma; a milky juice which may be scraped from the cut surface, to carcinoma or highly cellular sarcoma (usually of the round-celled variety); and the appearance of plugs resembling comedones on lateral pressure upon the cut surface, to epithelioma.

When the juice of the tumour is examined microscopically there are found, in case it is derived from a carcinoma, large polymorphic epithelioid cells with large vesicular nuclei and distinct nucleoli, which in part lie singly, in part are tightly rolled up into round or cylindrical groups, with or without pearl globules; but in this case the juice must always be taken from the interior of the tumour. If, on the other hand, a sarcoma is being dealt with, the juice, except in the case of large-celled sarcomata, will contain only comparatively small cells, the great majority of which are rounded or spindle-shaped, or it will be rather poor in cells of any kind.

Although a tolerably definite diagnosis may not unfrequently be arrived at even by this method of investigation, still as a rule sections ought also to be examined, especially when the problem is to ascertain whether the tumours present are malignant. Such sections are made from fresh specimens, or from the tumour after hardening, and should always be taken from the youngest portions, as free as possible from retrograde metamorphoses.

CHAPTER V.

THE PARASITES.

I. VEGETABLE PARASITES.

1. Introductory. By the term Parasites are understood those living creatures which vegetate in or upon another living organism, and at its expense. The injury inflicted on the host by the parasites is sometimes very slight, but in other cases considerable local troubles arise, and in others again severe general symptoms may even be caused. The parasites of man are derived partly from the vegetable and partly from the animal kingdom, belonging in the former case to the Bacteria, Yeasts, and Moulds, in the latter to the Protozoa, Vermes, and Arthropoda.

4. BACTERIA [SCHIZOMYCETES].

2. General Bacteriology.-Bacteria are excessively minute unicellular organisms, for the most part destitute of chlorophyll, which often unite to form combinations or colonies.

The bacterial cell consists of a [protoplasmic] substance and a surrounding membrane, the former of which behaves towards stains as do the cell-nuclei of more highly organised beings; but whether structures resembling nuclei really exist in the contents of the bacterial cell has not as yet been certainly made out.1 The membrane is properly speaking only the condensed innermost layer of a gelatinous envelope surrounding the cells, which is recognisable in many bacteria both with and without staining, and is then termed a capsule (Plate IV., Fig. 1).

Although it is not possible at the present moment to undertake a classification of the bacteria which shall rest upon a natural basis, still there can be no doubt whatever that there are amongst them well-characterised genera and species which do not merge

[Some believe the protoplasmic body to be itself the nucleus].—Tr.