152 M. R. KING 



method to the sheath of the S.V.S. according to Lhamon occurred 

 to Dr. Meyer, at whose suggestion Lhamon, working on beef 

 hearts, in 1912 easily succeeded in demonstrating the S.V.S. 

 in situ from the main trunk to many of its terminal branches. 

 Lhamon 's excellent injections supplied us with a new and reli- 

 able means of study. By it one is enabled to get a good idea of 

 the shape and ramifications as well as a lasting impression of the 

 exact position of the system at least in the hearts of Bos taurus, 

 Ovis arises and Sus domestica. For although models made by 

 reconstructions and dissections have given a good idea of the 

 shape and main ramifications they fail to give one a compre- 

 hensive view of the bundle in situ in the heart. A reference to 

 Lhamon's figure and those accompanying this article will quickly 

 make this evident. 



The presence of a definite sheath around the S.V.S. is in per- 

 fect harmony with what we know of the other organs of the body. 

 The muscles, bones and nerves have their sheaths, and the kid- 

 neys and spleen also have connective tissue capsules all of which 

 serve as dividing lines keeping the parenchyma of the enclosed 

 organs from coming in direct contact with the tissues of adja- 

 cent organs. Indeed, there are no naked or uncovered organs 

 in the body. 



Sheaths in general are closely applied to the enclosed organ 

 or more or less loosely attached. The nerve trunks have loose 

 sheaths which may be distended by injection mass. Key and 

 Retzius '76, for example, were able to apply the injection method 

 using Richardson's solution, for demonstrating nerve sheaths. 

 These observers obtained pictures similar in some respects, to 

 those produced by injection of the sheath S.V.S. 



This investigation was limited almost exclusively to beef 

 hearts. Ninety hearts obtained from an abattoir in San Fran- 

 cisco, were used and although twelve to fourteen hours had 

 usually elapsed before they reached the laboratory they proved 

 to be entirely satisfactory for injection purposes. Although on 

 a few occasions several hearts could not be utilized until after 

 seventy-two or more hours had passed, yet it was found that they 

 invariably gave as good if not better results with the injection 



