True hypertrophy appears, a priori, incontestable, and numberless instances have been recorded of its occurrence in every part of the body. It is remarkable, however, that when tested by an analysis, with reference to elementary texture and development, the proof is attended with extraordinary difficulty as regards the most important organs and tissues.

When it is the question, not of an obvious augmentation of the less important components of an organ - for example, of the areolar, the fibrous, the adipose tissues - but of a multiplication of the essential structural elements, the positive proof by elementary analysis often fails, although, both before and after death, the characters of the organ may seem quite sufficiently exaggerated to warrant the assumption of true hypertrophy.

Apart from a development of substance resulting from extraordinary succulence of the texture - that is, from its imbibing an excess of amorphous plasma more or less rich in nutrimental substances - hypertrophy can only depend either upon a multiplication of the essential textural elements by an accession of new ones, or else upon an enlargement of the original ones. Upon this point a generalization is not feasible at the present day, and it must suffice to set forth in due succession the results of researches touching special hypertrophies.

We may specify, as unquestionable, hypertrophy of the areolar, of the fibrous, and of the adipose tissues; of the common integuments, including, not alone the cutis and the papillary bodies, but also the sebaceous glands and the epidermidal formations; of the mucous membranes and their follicles; and lastly, of the bones.

Hypertrophy cannot indeed be demonstrated by a comparative enumeration of the form-elements; and the size of the latter varies considerably even in the physiological state. Where, however, the increase of mass is obvious, and there is no accession of heterogeneous elements, the sum of the primitive form-elements must needs have become multiplied, and hypertrophy exist. We find, too, in the involved textures - for example, in areolar tissue - an extraordinary number of the elements in their embryonic stages.

Hypertrophy of muscle, however simple it may seem, is in reality most difficult of proof. The increase of mass and volume in a hyper-trophied muscle certainly seems due to augmentation of its amount of fleshy fibres; positive evidence, however, at least with respect to the striated muscles, has hitherto been wanting. An enumeration of the primitive fibres is not feasible, nor have elements obviously engaged in the embryonic phases of new muscle-formation been as yet detected. Still less has an enlargement of the primitive muscular fibres, through increase in the amount of their primitive fibrils, been made out. That the hypertrophy consists simply in the augmented growth of the myolemma is disproved by the saturated dye, the extraordinary resiliency, the functional energy, for example, of a hypertrophied biceps brachii. Least of all could it be explained on the ground of augmented fat formation - the effect of excessive development of fat, in whatever shape, being to repel the growth of muscle. The last two propositions are moreover refuted by the hypertrophy of organic muscles.

The examination of hypertrophied hearts, for which the opportunity is frequent, offers but little assistance towards the solution of the problem, more especially where the increase of mass is considerable. A new accession of muscular fibres is not manifest. On the contrary, in proportion to the diminished energy of the organ, their fibrils are found in the progress of reduction to a partially dark-colored molecule, and of gradual extinction. One thing alone is evidently adventitious, namely, irregular aggregations of an amorphous fibro-laminated blastema, copiously interspersed with nuclei in different grades of development into areolar tissue, and of areolar tissue itself, together with a large proportion of free fat and of adipose tissue.

In the hypertrophy of organic muscle the characters are more clearly defined. Here, along with nuclei, we meet with little, flat, elongated, and nucleated bodies, the rudiments of new fibres. A marked instance of hypertrophy of this nature is afforded, amongst others, by the pregnant uterus, which, at the same time, exemplifies the disintegration of fibre, and the lingering of a multiplicity of nuclei, which are themselves eventually absorbed.

Even hypertrophy of the nervous system is little more than a problem. The development of fresh nervous filaments is unproved and even improbable. Nor is the enlargement of the nerve-tubules through increase of their contents more readily demonstrable. In the central organs, and particularly in the brain, the anomaly consists in an accumulation of the minute granular connecting mass interstitial to the nerve-tubules. At the circumference it can consist only of an augmentation of the neurilemma. In the ganglia the accession of new ganglion-cells, though not ascertained, is rendered probable by the regeneration of excised ganglia.

One of the hypertrophies most frequently discussed is that of glandular bodies. We shall pass over, for the present, the false hypertrophies so frequent, particularly in the liver, the spleen, and the kidneys. That of other - for example, the mammary, the salivary - glands may consist in an augmentation either of some constituent of secondary importance - for example, areolar or adipose tissue - or of the parenchyma itself; and it is with evidence respecting this last form that we are here principally concerned.

Examined with the naked eye, the parenchyma of the enlarged prostate gland, as that best adapted for this experiment, certainly appears to have undergone an increase of mass. This might be brought about either by the creation of new acini (lobules), or by the enlargement of existing ones, through the apposition of fresh enchyma-cells; or, lastly, by the co-operation of both. The appearances in hypertrophy of the prostate gland render the new formation of lobules and of lobes highly probable. Henle's observations, however, of the existence of solitary enchyma-cells in the vicinity of the glandular lobules in the lachrymal gland of a calf, and still more, what is very readily witnessed, in hyper-trophied thyroid glands, render probable the new formation of such gland-cells, and, through the resorption of their partition walls, their blending with the lobules so as positively to enlarge these.

A peculiar kind of hypertrophy, concurrent with dilatation of the cavities of the acini, is a very frequent cause of the enlargement of glandular formations. This dilatation is due to an augmented secretion taking place within the follicles, determined by the same local or general causes as the hypertrophy itself; and this latter consists in an increase of mass in the investing fibres of the follicles. This condition is immediately followed by the expansion or degeneration of the follicle to a dilated cyst-like cell, with a stouter lamina of enveloping fibres. At the same time the secretion may become alienated both in quantitv and in quality, until a cyst is completed with contents altogether alien to the native secretion of the gland. This is witnessed in the follicles of the thyroid gland, in the Malpighian bodies of the kidneys, in the Graafian follicles, and in the acini of the salivary glands; in the mucous follicles, particularly those of the cervix uteri, where, even in the physiological state, they frequently dilate into capacious, thick-coated cysts, rupture, and discharge their contents.

Evidence of hypertrophy of the liver, of the spleen, of the lymphatic glands, is hardly obtainable.

The idea of a hypertrophy of the liver from the accessory formation of new hepatic cells would not indeed be discordant with our notions of the functional importance of that organ. All anatomical proof is, however, unattainable. That, on the other hand, upon which it more obviously depends, is turgescence of the hepatic cells from an increased proportion of fat and of bile, together with hyperemia of the capillaries. This condition determines the more or less marked development of what is called the secreting substance of the liver, - one-sided hypertrophy of the liver, as it is termed, or nutmeg liver.

Hypertrophy of the spleen must be referred, first, indeed, to the reinforcement of its fibrous framework, but mainly to augmentation of the pulpy parenchyma of the spleen, that is, of the elements out of which it is constructed.

Nor can hypertrophy of the lymphatic glands be well traced to the adventitious development of new lymphatic vessels between their parenchyma, but rather to increase of the parenchyma between the lymphatic vessels. It is certain, at least, that in atrophy, the lymphatic vessels become deficient in parenchyma.

Hypertrophy of the lungs consists not in the addition of new cells, but in an augmentation of matter in the parietes of the existing ones. The ample, energetic (vicariating) function, moreover, of a hypertrophied lung seems to imply a multiplication of the capillary vessels by the creation of new ones. Thus, again, hypertrophy of the corpora cavernosa does not depend upon the addition of new cellular spaces, or their increase through the development of new septa, but upon increase of substance, thickening of the walls of the cellular spaces, with simultaneous dilatation of these latter.