The causes of hypertrophy are:

1. Morbid Increase Of The Quantity Of Blood

Morbid Increase Of The Quantity Of Blood in the capillaries of, and retarded circulation in, the affected organ; repeated and abiding hyperemia. Examples are furnished in particular by the frequent hypertrophies of the abdominal viscera arising out of mechanical hyperemia, of the mucous membranes in organic diseases of the heart, of the areolar tissue in the lower extremities in a varicose condition of their veins, and, lastly, by the hypertrophies of the mucous membranes brought about by the hyperemia entailed by repeated inflammation.

2. Augmented, Violent Action

Augmented, Violent Action induced by various direct or reflected stimuli. Examples present themselves in hypertrophy of the voluntary muscles, of the heart, of the organic fleshy tunics.

3. The Groundwork Of A Lengthy Series Of Hypertrophies

The Groundwork Of A Lengthy Series Of Hypertrophies consists in a constitutional vice of nutrition and in an anomalous blood-crasis. The hypertrophy is here the expression, th$ symptom, of general impairment. This applies to true, and with greater force to false hypertrophy. To this class belong hyperostosis, excessive development of fat, endemic goitre, - hypertrophy of the brain, and hypertrophy of the lymphatic glands in rhachitism, - the excessive development of fat with simultaneous impairment of its quality in alcohol-dyscrasis, - the conditions of fatty, of waxy liver, of brawny infiltration of this organ, of the spleen, of the kidneys in tuberculosis, rhachitisms, inveterate syphilis, etc.

4. Inflammation

Inflammation; the result of which is so-called inflammatory hypertrophy, to which we shall have to recur by-and-by. It engenders true hypertrophy in areolar and osseous textures alone; in all the rest, through the fresh deposition of areolar and of fibroid tissues, false hypertrophy.

Hypertrophies of both kinds are either congenital, or, what is far more frequent, acquired during extra-uterine life.

The course of hypertrophies is for the most part chronic. Nevertheless, they not rarely form within a surprisingly short period, or from time to time rapidly increase. They are then often painful affections, as, for example, the acutely developed fatty liver.

Hypertrophy, when it has attained a high degree, impairs the function of the affected organ, whilst the latter, by its increase of weight and of volume, obstructs the function of neighboring parts.

Of itself it commonly proves fatal through palsy, the result of the ultimate disproportion between the bulk of the hypertrophied organ and the powers of innervation. As examples may be cited hypertrophies of the heart, palsy of the hypertrophied intestine above a stricture, palsy of the hypertrophied urinary bladder, and the like.

A proper discrimination is requisite between increase of volume from hypertrophy and the dilatation of hollow organs, more especially if associated with attenuation of the parietes. Dilatation is generally coupled with hypertrophy of the walls of the dilated organ, - termed active dilatation, co-significant with excentrical hypertrophy. Simple dilatation, in which the walls are of their natural thickness, is a kindred form. Dilatation may, however, be conjoined with attenuation of the walls; it is then denominated passive dilatation. * The causes of the dilatation of hollow organs are various.

1. Mechanical Impediments

Mechanical Impediments, which obstruct the free passage and egression of the contents of the different canals and reservoirs. They occasion dilatation either beyond or behind their seat, and manifest themselves -

(a.) As local constriction of calibre, through pressure from without.

(6.) As coarctation consequent upon hypertrophy and change of texture in the walls of the organ. In instances rare, except in disease of the heart, as dilatation. Thus, whereas in the intestinal canal it is the accumulation of its contents, on the other hand, in dilatation of the orifices of the heart it is the increased diameter of the blood-column, in insufficiency of the heart-valves the regurgitation of the blood, that furnishes the mechanical impediment.

(c.) As obturation of canals with substances of various kinds, whether introduced from without or begotten within the organism, whether closing up by their bulk or obstructing by their aggregation, - in a word, as foreign bodies, secretions, etc.

Other local causes, however, besides the above-mentioned - accumulations of foreign bodies, of self-engendered deposits - are in like manner productive of dilatation.

2. Paralysis Of The Contractile Elements

Paralysis Of The Contractile Elements in the walls of the organ, whether peripherous, and consecutive to mechanical, concussive violence, tension, etc, to disease of texture, especially inflammation; or determined by affection of the nervous centres.

3. Diseases Of Texture

Diseases Of Texture; for example, fatty degeneration, particularly of the heart.

4. Inflammations

The different causes frequently act in unison in various sequences. Thus, coarctation begets accumulation of contents. This, together with a certain relative amount of existing dilatation, occasions paralysis of the organ. The paralysis causes dilatation, and thereby accumulation of the contents, which again, in turn, mechanically promotes the dilatation.

Dilatation destroys life through paralysis, either simply or with the concurrence of asthenic stasis, inflammation, and gangrene, towards the establishment of which the contact of retained contents in the progress of decomposition contributes its part. Take for example the intestinal canal, the urinary bladder, etc.

Sudden dilatation is wont to assume the passive character, a supervenient hypertrophy being more marked in the inverse ratio of the celerity with which the dilatation is brought about.

Increase of volume in one direction at the expense of the general bulk of the organ, the result of forcible tension, is distinct from hypertrophy.