ATROPHY. 445 



being expressions of the same power, the simple cyst being a kind of rude 

 attempt at the production of a distinct individual, and the encysted em- 

 bryo being but the result of au unusually high development of a proliferous 

 cyst. 



359. The state of Atrophy is in all respects the very opposite of that of 

 Hypertrophy ; consisting in such a reduction in the rate of formative ac- 

 tivity of the parts, as compared with that of their " waste," that their nutri- 

 tion is no longer maintained at its previous standard ; so that they are gradu- 

 ally reduced in bulk, or degenerate into some inferior histological type, or 

 (which is more common) undergo both diminution and deterioration at the 

 same time. It is important to bear in mind, that Atrophy may take place, 

 either locally or generally, from au unusually rapid disintegration of the 

 tissues, uucompeusated by a corresponding increase in the rate of their 

 nutrition : of such local atrophy, we have a characteristic example in the 

 rapid reduction of the bulk of the uterus after parturition, and of the mam- 

 mary glands after the sudden cessation of lactation ; of the general, we see 

 au illustration in that rapid wasting of the system, which takes place in the 

 irritable state that results from excessive and prolonged exertion of body or 

 anxiety of mind, especially when accompanied with want of sleep, the in- 

 creased disintegration being marked by the presence of an unusual amount 

 of urea and of the alkaline phosphates in the urine. But in the ordinary 

 forms of Atrophy, there is not merely a relative but an absolute reduction in 

 the rate of the formative process, or a lowering of its standard of perfection ; 

 and here also we have to look for its causes, on the one hand, in the condi- 

 tion and supply of the blood, and on the other, in the formative capacity of 

 the tissues themselves. The Atrophy dependent upon an insufficient supply 

 of nutritive materials, may be either general or partial. General atrophy, 

 or emaciation, is a necessary result of deficiency of food ; but it may also 

 proceed from an imperfect performance of the assimilating processes, whereby 

 the nutritive materials do not receive their requisite elaboration, as in cases 

 .of disease of the mesenteric glands ; or from an unusual energy of the meta- 

 morphic processes, whereby the azotized constituents of the food are decom- 

 posed into excrementitious products, without undergoing assimilation at all, 

 as seems to be the case in diabetes. Of the atrophy of a particular tissue, 

 consequent upon the deficiency of its proper materials in the blood, we have 

 an example in the reduction of the adipose, when there is no surplus of 

 fatty matter to serve for its nutrition, but on the other hand, a withdrawal 

 of the contents of the fat-cells into the circulating current, whilst the nutri- 

 tion of the muscular and other azotized tissues may proceed with its usual 

 vigor. Instances of complete local atrophy, or gangrene, resulting from 

 deficiency in the supply of blood to a part, are by no means unfrequent ; 

 but it is less common to meet with a prolonged diminution in the rate of 

 nutrition from such a cause, since a partial obstruction to the circulation is 

 usually removed after a short time by the enlargement of the collateral 

 vessels. Yet there are peculiar circumstances under which this does not 

 take place; thus Mr. Curling has shown that atrophy may occur in that 

 portion of a fractured bone which is cut off from the direct supply of blood 

 through the great medullary artery ; the circulation being restored by anas- 

 tomosis to such an extent as to prevent the death of the bone, but not so 

 completely as to support vigorous nutrition. 1 



360. The most frequent cause of Atrophy lies, however, in the deficiency 

 of formative power in the tissues themselves, arising from the decline of 

 that capacity which they inherit from the germ. This decline, as already 



1 Medico-Chirurgical Transactions, vol. xx. 



