structure, having like functions, with the relatively complex, specialised, and heterogeneous parent-tissue, there truly comes into view the exemplification of dissolution we have sought.

The later transformations through which the germs pass in the process of development, conform, we have found, to evolution, and it remains to refer to the retrogressive changes. Those met with in tumours are of the same kind as the degenerations of normal tissues, and as such they have already been considered. Therefore, all that is required here is their enumeration. They are calcification, caseation, and softening; colloid, mucoid, and fatty degeneration. Tumours are also liable to hæmorrhage, ulceration, suppuration, and decomposition.

The morbid affection set going in the organism by the expansion of a new growth within its substance may be an inflammation or irritation followed by the development of cicatricial tissue in surrounding parts; it may be an extension of the neoplastic change to normal tissues from the influence of the tumour-cells; or it may be a reproduction of the growth in distant places due to the dissemination of these cells by lymphatic, blood-vascular, and other channels. From what has gone before it will be seen at once that all these changes are comprehended by the principles of evolution and dissolution.

Neoplasms interfere with the functions of organs. A tumour in the spinal cord will give rise to disorders of motion and sensation; in the stomach, to disorders of digestion; in the bladder, to disorders of vesical function. And there is the cancerous cachexia, the

components of which are systemic and recondite alterations in the physiological processes of the body. As seen from the point of view of the principle of dissolution, this class of disturbances consequential to the diseases under consideration may be more conveniently instanced in succeeding chapters, especially since the pathology of cancerous cachexia is too indefinitely understood to admit of separate treat

ment.

§ 3. THE CYSTOMATA, TERATOMATA, AND

MALFORMATIONS.

The very many modes of origin of cystomas, and our ignorance in manifold cases of the conditions of their formation, quite preclude such references to the formulas as we might rest content with. Glancing first at retention cysts, those due to the confinement of normal secretions within pre-existing cavities, doubt arises whether this disease can truly be called a dissolution. Sebaceous cysts-wens, for example— are not obviously accompanied by disintegrations of matter; rather is matter integrated. This is strikingly the case of the curious horns growing from sebaceous tumours. It seems possible to effect a reconciliation with the formula of dissolution only by regarding the contents of the cavities as the accumulated products of normal processes of dissolution. The epithelial scales, fatty matter and cholesterine of sebaceous cysts, are excrementitious elements collecting from closure of the excretory ducts; and the horns just alluded to are nothing more than exfoliated epidermal cells dried and hardened by exposure to the air.

It coincides with dissolution that the disease is sometimes caused by inflammation and excessive activity of the sebaceous glands. Unhealthy matters finding outlets through these channels provoke hypersecretion and inflammatory closure of the cutaneous openings. Congenital piliferous cysts, which resemble sebaceous tumours but are congenital and have fully developed hairs growing from them, rather belong to the order of neoplasms.

Cysts arising from the retained secretions of mucous glands, as the glands of Bartholin and Cowper, and also galactoceles, probably originate in the same way as sebaceous tumours. Ranulæ, from occlusion of the ducts of salivary glands, are oftentimes connected with the impaction of a calculus, and with the irritation of bits of vegetable fibre and fruitseeds derived from articles of food. New growths, calculi, and parasites are among the causes of pancreatic ranulæ, biliary cysts, and hydronephrosis.

The cystic kidney of chronic nephritis, where there is ectasia and dilatation of urinary tubules, must be referred, remotely, to the causes of the latter disease.1 Congenital cystic kidneys are now thought by some observers to depend upon the degeneration of persistent fatal structures, e.g., the Wolffian body, and not upon the congenital absence of the pelves of the kidneys.

Dilatation of the vermiform appendix, leading to a cystic tumour of this structure, commonly results from closure by foreign bodies or inflammation at the

1 See Part II. chap. v. § 2.

opening into the cæcum. The causation of cysts of the vitelline duct and urachus is very obscure.

In this form of cystic disease, then, the indications of dissolution are exceedingly weak; only here and there can we detect an initial disintegration of matter and concomitant absorption of motion. Perhaps by an examination of each example in all possible detail a less incomplete correspondence might be effected. But, by the formation of these tumours, we may legitimately say that the organism sustains a loss in the federation, expressness, and variety of its functions and structures.

Exudation cysts call forth similar comments. In these there is excessive secretion in cavities not provided with an excretory duct. The slighter forms of certain examples (bursa and ganglia) are not diseases, but adaptations of structures to simple increase of function. The enlargement of bursæ and ganglia is the result of increased action of tendons and muscles. When the actions are excessive, and other conditions are favourable, inflammatory dissolution may ensue, which in numerous familiar examples is the clear effect of communicated motion. Ganglia of the extensor tendons of the hands in pianists, the swelled bursa patella of housemaids, and miner's elbow are cases in point.

Most cystomata connected with the brain, spinal cord, and their membranes are cases of malformations by arrest, and will presently be mentioned with these affections. Naming them here, they are anencephalia, meningocele, encephalocele, syringo-myelus, and the varieties of spina bifida.

Many of the cysts in structural relation with the organs of reproduction rehearse the truth we had occasion to note in the chapter on new growths, namely, that 'obsolescent remnants' are eminently disposed to neoplastic degeneration. Relics of the mesonephros, or Wolffian body-an ancestral excretory organ-persist in the hilum of the human ovary; the tubules of the mesonephros within the folds of the broad ligament are known as the parovarium. It is a credible presumption that these relics are the sources of what are spoken of as ovarian papillary and parovarian cysts, and, in the male, as encysted hydrocele.

The duct of the mesonephros-Gartner's ductopening into the vagina, is almost certainly concerned in cystic formations. Mr. Bland Sutton has brought forward an impressive array of facts to show that numerous cystic growths of the ovarian parenchyma start in the arrested normal decay of ovarian follicles. There is hardly any doubt that one of the conditions of the genesis of true tumours obtains with these cystic new formations in diseased parts. And it seems as likely, from the observations and reasoning of Dr. W. O. Priestley, F.R.C.P., LL.D.,1 upon the genesis of cystic chorion—the so-called hydated mole -that cysts of this class are true tumours; that they originate from asexual reproduction of normal cells; and that, some of the new generation undergoing retrogressive changes which bring them to the fluid

1 The Lumleian Lectures on the Pathology of Intra-Uterine Death. British Medical Journal, No. 1371.