252 THE HEART, BY F. SCHWEIGGER-SEIDEL. 



has been made perpendicularly to the axis of the heart. These 

 statements are true at least in regard to the endocardium of 

 the septum ventriculorum of man, in which smooth muscular 

 tissue is very distinctly visible. * Moreover, the more exter- 

 nally situated transversely striated muscular tissue of the 

 endocardium does not form a continuous or uniform layer, on 

 which account it may easily be overlooked, or may be regarded 

 as belonging to the muscular layers in general. That the 

 latter is not the case, however, is obvious from the circum- 

 stance that the muscular elements in part possess special 

 peculiarities, and also that the endocardial layer is separated 

 from the general musculature of the heart by connective 

 tissue, lymph vessels, and networks of nerves. 



Moreover, we find in the endocardium per se all the usual 

 layers entering into the composition of the vascular walls, and 

 may therefore very correctly, with Luschka,f identify the endo- 

 cardium with the whole vessel, and not simply with its tunica 

 intima. It remains to be remarked that the above statements 

 are not applicable to the auricles, since their endocardium, 

 although it possesses considerable thickness, and is remarkably 

 rich in elastic tissue, does not present any proper muscular layers, 

 though here and there a few smooth muscle cells are discoverable. 



The transversely striated muscle of the endocardium of 

 the ventricle occurs in two forms, either as the well-known 

 Purkinje's fibres, or as a wide-meshed network of muscular 

 bundles, the elements of which are distinguished from those 

 of the heart by their proportionate size, being broader and 

 shorter. As regards the grey gelatinous-like fibres recog- 

 nisable by the naked eye, which Purkinje described in 1845 

 as being situated under the endocardium of the calf, they 

 must partly be considered as a peculiar motor apparatus, 

 and partly as an embryonic form of the muscular tissue 



* Kolliker denies positively the presence of smooth muscular tissue in 

 the endocardium (Mikroskopische Anatomie, Band ii., p. 493). Nevertheless, 

 in regard to the localities referred to, no doubt can exist of the correctness 

 of my statement. 



t Virchow's Archiv, Band iv., p. 171 ; and Anatomie, Band i., Abth. 2, 

 p. 380. 



