I'acunm, Xcn'ous, / iillniiiiitatory 11 ypcrtroplix. 257 



canals (vessels, intestine, nrinarx- liladder or i^iillet ) . the cause in 

 such instance always heing a retention of the contents ( increase 

 of blood pressure, influence of calculi, obstruction to the movement 

 of tlie chyme, etc.) causing primarily distension of the lumen of 

 the part and stretching of the muscular wall. 



That a diminution of the factors of resistance of growth, of tissue 

 resistance, favors hypertrophy (z'aciiuin hypertrophy) is apparent 

 in the liver in case of the existence of a diaphragmatic cleft ; the 

 liver tissue invariably grows through such an opening, and, just as 

 a button goes through a liutton hole, forms a new liver lobe pro- 

 truding into the thorax, the soft and elastic lung tissue ofifering but 

 little opposition. Such intrathoracic hepatic lobes may sometimes 

 be found larger than a fist (in sheep, cattle, swine). 



[The influence of nervous factors in some cases of hypertrophy 

 can scarcely be doubted, although it is probable that for the most 

 part such influence operates in ways conforming with the causes 

 above mentioned. The ability to take up and assimilate nutrition 

 is in relation with the trophic influence of the nervous system, and 

 the condition of the vessels supplying nutrition has even more ap- 

 parent dependence upon the nervous functions ; and so, too, the rela- 

 tive tone or the opposite condition of relaxation of tissues is regu- 

 lated by nervous factors. Variations in functional activity are often 

 determined by nervous influences. Leaving aside such influences 

 in which perhaps the nervous factor may determine hypertrophy 

 by evident involvement of such influences as increase of blood sup- 

 ply, the provision of mechanical relaxation of tissue or the stimu- 

 lation of functional activity, there are more obscure examples (pos- 

 sibly in the end explicable on the same grounds but not clearly 

 showing such reasons for growth) which for the time are properly 

 spoken of as nervous hypertrophies, as the enlargements in acro- 

 megaly, for example, or the papillary enlargements of the skin in 

 many warts.] 



Connective tissue hypertrophies are usuall}- the result of chronic 

 inflammation and chronic passive hyperaemia. in either of which 

 there are features of tissue destruction and of tissue dilatation. 

 Where the liver becomes enlarged and the seat of connective tissue 

 induration from chronic inflammation there occurs primarily a de- 

 struction of the liver cells and a coincident growth of the support- 

 ing tissue ; the termination of chronic lymphangitis of the cellular 

 tissue of the foot in pachydermia (rufifle foot or bristle foot in the 

 horse) may be explained by the idea that at first the connective 

 tissue spaces are filled with lymph and exudate and later become oc- 



