558 OF NUTRITION. 



But further, in many of the large class of tumors distinguished as " malignant" 

 ( 616), the development of tissue has not gone to the extent of producing any 

 of those species of which the body is normally constituted ; and in this respect 

 as well as in their tendency to rapid degeneration, the vital endowments of their 

 elements must be reckoned as below those of the normal tissues. It is not 

 always easy to draw the line between certain tumors and supernumerary parts, 

 especially when the production of the former is symmetrical ; but the first ap- 

 pearance of the latter never takes place save during embryonic life, and their 

 structure is more complex, and is more conformed to the plan and construction 

 of the body at large, than is that of tumors, whose production may take place 

 at any period of life. And between those tumors which are known as " pili- 

 ferous" and " dentigerous cysts," and those encysted embryos (usually incom- 

 plete in their formation) which are sometimes found in the bodies even of males, 

 it is impossible to establish any line of demarcation sufficiently precise to prevent 

 our recognizing them as all having the same origin and 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 embryo being but the result of an un- 

 usually high development of a proliferous cyst. 



598. The state of Atrophy is in all respects the very opposite of Hypertrophy; 

 consisting in such a reduction in the rate of formative activity as compared with 

 that of their u waste/' that their nutrition is no longer maintained at its previous 

 standard ; so that they are gradually reduced in bulk, or degenerate into some 

 inferior histological type, or (which is the more common occurrence) 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 an un- 

 usually rapid disintegration of the tissues, uncompensated by a corresponding 

 increase in the rate of their nutrition ; of the former we have a characteristic 

 example in the rapid reduction of the bulk of the uterus after parturition, and 

 of that of the mammary glands after the sudden cessation of lactation ; of the 

 latter we see an illustration in the 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 

 increased 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 condition 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 neccessary 

 result of deficiency of food; but it may also proceed from an imperfect perform- 

 ance 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 metamorphic processes, whereby the azotized 

 constituents of the food are decomposed 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 cur- 

 rent, whilst the nutrition 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 nutri- 

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



