162 M. R. KING 



into the four classes mentioned for the S.V.S. The branches 

 of the S.V.S. follow the ridges of the trabeculae carnae and thus 

 acquire a distribution similar in arrangement to them. 



The general conception of the arrangement of the sheath of 

 the S.V.S. is that it consists merely of an enveloping connective 

 tissue layer which extends in among the fasciculi. As a matter 

 of fact the sheath is more complicated than this. In each of 

 the main branches which bear typical sheaths the following 

 description holds. The fibres or cells of the S.V.S. are grouped 

 into bundles, the fasciculi. Each fasciculus is surrounded by a 

 definite sheath of connective tissue derived from the common 

 enveloping sheath. The structure of the fascicular sheath is 

 very constant and the degree of condensation remains the same 

 in all .the specimens examined. This cannot be said of the 

 general sheath, however. This is made up of loose connective 

 tissue even approaching areolar tissue in some portions, while in 

 other parts a more or less condensed connective tissue is found. 

 This sheath carries the blood vessels, nerves and lymph vessels. 

 Because of the absence of any better term the name epifas- 

 ciculum will be applied to the general enveloping sheath while the 

 sheath surrounding the individual fasciculi will be designated 

 as the perifasiculum. The perifascicular sheaths are in close 

 contact with the enclosed fasciculi but are not firmly attached 

 and may hence be distended by the injection mass. 



The epifascicular sheath can be identified only on the main 

 branches. In the terminal network the fasciculi are not bound 

 together into bundles but in many cases run as single fasciculi. 

 This fact accounts for the real fine networks seen in many places 

 on the ventricular walls. Where several fasciculi are held close 

 together they present a coarser network. Often single fasciculi 

 shoot off from the bundles thus producing delicate fine inter- 

 lacements very similar to delicate nerve plexuses. These termi- 

 nal fasciculi, however, always retain their perifascicular sheaths 

 which are as capable of holding the injection fluid as any found 

 in the main branches. 



Anyone studying the sheath of the S.V.S. cannot help but 

 notice the similarity to the sheaths of nerve trunks. In the 



