272 CIRCULATORY APPARATUS. 



individual fibres grow thicker, is very generally received. Never- 

 theless, I have failed to discover any difference in the thickness 

 of the muscular fibres of hypertrophied hearts ; so that I have at 

 last been led to assume that a "partial splitting" of the fibres 

 must occur ; an assumption which can only be admitted as 

 regards the heart. 



The muscular fibres of the heart, as every one is aware, 

 divide dichotomously ; they may also be said to reunite in 

 the same way, forming networks or membranes with elongated, 

 slit-like meshes. These meshes vary greatly in their size ; large, 

 spindle-shaped lacuna3 alternating with slits and fissures of the 

 smallest size. Some of the latter may even be regarded as 

 situated in the substance of individual fibres. They are most 

 frequently found in the thicker fibres, where these give off lateral 

 branches (hg, 85, a) and I cannot but believe that the force 



Fig. 85. 



Network of niiisciiliir ilbi cs from the heart. At a is an inter- 

 stice in a muscular hbre, which corresponds in position to 

 the origin of a side branch ; by its gradual increase in size, 

 it will add a new mesh to the network. 



exerted by the side-branch during its contraction contributes 

 in some measure to the cleavage of the parent-fibre. 



B. Atroplifj of the Heart. 



§ 23G. Inasmuch as the heart is undeniably the hardest- work- 

 ing muscle in the body, and therefore consumes more nourish- 

 ment than most other organs, disturbances in the general nutrition 

 of the organism will necessarily make themselves felt in the heart 

 at a relatively early period. Not only the involution of the body 

 due to old age, but every cachexia, every form of marasmus, 

 whether due to acute or chronic disease, may thus cause wasting 



