In this chapter we have to treat of:

A. Pneumatoses and Dropsy, which we have already adverted to as non-organized new formations.

B. Foreign substances introduced into the body.

C. Parasites, that is animals, and vegetable growths, occurring in and upon the living body. We give them a place in this chapter because, according to the researches of modern science they are to be numbered amongst the things that are received into the organism from without.

A. Pneumatoses And Dropsy

1. Pneumatoses, - the accumulation of various gases has been observed as emphysema, both within textures, and more particularly in almost every cavity of the body and of its organs. The scale of frequency varies, indeed, according to the nature of the gas, and to its mode of origin. There are, however, organs in which gas-accumulations of every kind are extremely common; and again, others in which a development and accumulation of gas are under all circumstances very rare.

The modes in which gas-accumulations originate resolve themselves generally, into the following:

(a.) The gas accumulated in the texture or in the cavities of the body or of organs, is atmospheric air which has penetrated from without. This applies to most kinds of emphysema, and of gas-accumulations in the pleural sac, partly to those in the stomach, perhaps also to the rare instances of gaseous collections in the uterus, and in the urinary bladder; lastly, to the presence of gas in the blood after the lesion of veins, particularly those of the neck. Most examples of interstitial emphysema and of pneumothorax are the result of lesions of continuity, through either wounds or ulceration in the bronchial passages or in the lungs.

By tarrying in preternatural localities, the atmospheric air suffers a change similar to what it undergoes in the lungs, its oxygen becoming exchanged for carbonic acid, with the superaddition of aqueous vapor.

(B.) The Gases Are Products Of Decomposition

To this category are to be reckoned, besides those gas-accumulations arising out of putrefaction after death, a. Gas-development out of the blood-mass, from putrid decomposition of the latter; out of blood perishing through absolute stasis; finally, out of decaying normal textures or morbid products, for example, sloughing cancers, or exudates undergoing decomposition.

3. Gas-development in the stomach and intestines, the details of which concern special anatomy.

2. Dropsy, whereby we understand genuine serous dropsy, that is, a fluid mostly alkaline, in its purity colorless and limpid, and analogous in the quality of its ingredients to, although originally thinner than, the serum of the blood; a fluid which, apart from the accidental admixture of exudates, pus-cells, blood-globules, epithelia and the like, contains nothing beyond unorganized effusions of albumen, pigments, fats (cho-lesterin), and salts. Under no conditions has it of itself alone the significance of a blastema.

It consists, chemically speaking, of water, albumen, fat and extractive matter, and of salts, the chloride of sodium preponderating over the rest, namely, the carbonates and phosphates, of alkalies, and of alkaline earths. Generally speaking, its proportion of water is greater than that in blood-serum. The albumen is subject to the greatest fluctuation, down to an infinitesimal allotment.

This relation is liable to various and not unfrequent deviations.

A red coloration is due to blood-pigment.

A yellow, or yellowish-green coloration, to bile-pigment.

A whey-like turbidness, a milky-white appearance, may be owing to certain of the admixtures adverted to, such as epithelium, but especially fat, and to an albumen precipitated by an excess of water [relatively to the saline contents].

Sometimes the fluid has a faint acid reaction.

A notable proportion of albumen renders the fluid viscid, adhesive, synovia-like.

This albumen, for the most part, shows itself to be pure; and not to differ from that of blood-serum; or else it exists as albuminate of soda. It occurs, however, in certain other tolerably well-known, and without doubt in many other as yet unknown modifications.

Occasionally the dropsical fluid contains urea. The accumulation of the fluid in the textures constitutes oedema, of which species of infiltration every organ may become the seat. Its collection in cavities of the body, or of organs, constitutes the dropsies. Moreover, the serous effusion developed beneath the vesicated epidermis in erysipelas, in burns, and through the agency of cantharides, is deserving of general mention here.

The Mode Of Origin Of Dropsy

The Mode Of Origin Of Dropsy varies:

(a.) The purest dropsy arises from retention of the blood in the veins through mechanical hindrance to the circulation. Its extension varies according to the seat of the obstruction, being considerable in proportion as it affects the centres of the circulation. It is in all probability the veins, even the larger ones, which, in a dilated and thin-walled condition, suffer an out-throwing of dropsical fluid to take place from the blood. The exudation will be considerable, proportionately to the amount of hydraemia - that is, of the serous crasis - that prevails.

Dropsy

Dropsy is, without doubt, determined by the lymphatics in a similar way.

(b.) Nor is there any doubt that serous effusion takes place, in like manner, from the capillary vessels. This mode of occurrence applies to the dropsy resulting from general debility; to that arising in palsied parts; to that referable to hydraemia. Again, we may attribute to the same source that acute or chronic oedema consequent upon mechanical capillary hyperaemia, both active and passive; and, lastly, that oedema founded in a slight degree of stasis, or attendant upon consummate inflammation. Of the latter description are those outpourings of the blood-serum precursory to the genuine exudation of plasma in the inflammatory process; the oedema encircling areoe of inflammation; the aforesaid serous collections beneath the epidermis, in erysipelas, in burns, etc.

(c.) In fine, dropsical effusions are brought about by attenuation of the blood, - or the serous crasis, a condition frequently combined with the aforesaid causal influences.

The consequences of serous effusion vary greatly according to the nature of the organs or textures concerned, to the extent of the accumulations, to the acute or chronic form of their occurrence, and to their duration. The relation of the textures generally is of much interest. In acute dropsy the textures are in various degrees congested, reddened, and withal - more especially the lung texture - lax, easily torn; - very delicate textures, for example, that of the brain, softened and destroyed. In chronic, enduring dropsy, on the contrary, they are discolored, pallid, bloated with imbibed serum. Smooth membranes become turbid and dull, the contractile fibre paralyzed.

Dropsical fluid is either wholly or partially re-absorbed, or continues unchanged. In the second case, the watery part being first of all absorbed, it becomes concentrated to an albumen, a synovia, or a thin jelly-like mass.

In what manner the various oedemata and dropsies may become perilous, and eventually prove fatal, is sufficiently evident.