706 SPECIAL PHYSIOLOGY. 



ment of some particular tissue, or to excessive supply of blood, to over-exer- 

 cise of a part, or to some not understood tendency to an increase of size or 

 growth, by excessive enlargement or multiplication of the tissue-elements. 

 Muscular hypertrophy and hyperplasia are more common in the involuntary 

 than in the voluntary muscles. 



Neoplasia, or the formation of new growths, is referred to a perverted 

 nutrition. Its cause is unknown ; though it is attributed, with some proba- 

 bility, to the accumulation in the blood of some similar nutritive material or 

 pabulum, fitted to stimulate their formation, and support their growth and 

 nutrition. The resulting tumors are sometimes homoplastic or homologous, that 

 is, they exhibit a structure similar to that of some normal tissue ; or they are 

 heterologous or heteroplQStic, their structure being entirely unlike any healthy 

 texture. Fatty, fibrous, cartilaginous, and bony tumors belong to the former, 

 and tubercle, fibroplastic sarcomas, and cancers, to the latter variety of new 

 formations. These, when once formed, are the seat of continued nutritive 

 changes, more or less perfect and proper to themselves, and maintaining, in 

 the midst of interstitial changes, the character of the abnormal tissue-elements 

 of each growth. 



Atrophy, or the gradual or rapid wasting of a part or tissue, depends on 

 general defective nutritive activity, an unhealthy condition or deficient supply 

 of blood, want of exercise in a part, or loss of intrinsic nutritive power. 

 Atrophy may be general, as that which follows deficiency of food or actual 

 starvation, or partial and local, as that which occurs in the fatty tissue, when 

 no fatty, amylaceous, or saccharine food is eaten, and the blood is destitute 

 of fatty matter. 



Softening, induration, and degeneration, imply not only defective, but more 

 or less altered, nutrition. The first consists in a liquefaction of the tissue- 

 elements ; the second and third, in depositions, in or about them, of albumi- 

 noid or amyloid substance, or in an actual conversion of the proper albuminoid 

 or gelatin-forming material of the tissue, into fatty matter, a change not un- 

 frequently seen in muscular tissues, especially in those who indulge in alcoholic 

 beverages. In certain cas*es, fatty degeneration prepares a tissue, or some 

 morbid deposit, the result of inflammatory or perverted hypertrophic or hyper- 

 plastic action, for more easy absorption and removal from the body ; some- 

 times this and other changes destroy tumors, and so lead to exhaustion and 

 death. 



Inflammation is essentially an abnormal or altered nutritive process. It 

 commences in some altered relation between the nutritive qualities and reac- 

 tions of a tissue, and of the blood, or its exuded plasma ; the normal nutritive 

 changes are arrested ; the unused plasma soon becomes excessive in quantity ; 

 oiew products are stimulated into growth, including, essentially, cells formed 

 by multiplication of the pre-existing connective tissue corpuscles. Moreover, 

 the condition of the blood, and of the capillaries, very soon becomes changed ; 

 the blood becomes less fluid, and the vessels distended and enlarged, causing a 

 state of congestion ; the red corpuscles of the blood in the part, cohere, and at 

 last become motionless or stagnate, stasis being produced ; the white corpuscles 

 increase in number in the blood generally, owing, it is supposed, to over- 

 activity of the commencing lymphatics of the inflamed part. Lastly, the 

 nerves of the part are excited by these changes, and by the disturbance in their 

 own nutrition. The chief obvious results and evidences of inflammation are 

 swelling, redness, heat, and pain ; but these are effects, and not even essential 

 characters, for one or more of them may be, under certain circumstances, 

 absent. 



Inflammation may end favorably in resolution, which consists in the absorp- 

 tion of the exuded material, and of the new products stimulated to growth by 

 it. These may, however, undergo rapid increase, and form solid and morbid 

 plastic deposits, or fluid pus, abounding in corpuscles like the white blood 

 corpuscles, and so give rise to induration, inflammatory thickening, or suppu- 

 ration. Collections of pus, surrounded by plastic deposit, constitute abscesses ; 

 these, by progressive absorption of their coverings, may reach the surface, and 

 burst. A further result of inflammation is ulceration, which consists in the 

 molecular death, and gradual softening and falling away, of a highly inflamed 



