220 



THE VASCULAR SYSTEM. 



Fig. 140. 



are usually oval, and are unipolar or rarely bipolar ; sometimes two 

 cells exist in the same envelope, forming the ' twin-cells '' of 



Dog'iel (Fig. 141b II). Accord- 

 ing to the recent observations 

 of Lavdowsky and Dogiel each 

 cell receives one medullated fibre 

 and gives off a fine non-medul- 

 lated fibre ; the two run together 

 for a short distance, after which 

 the non-medullated fibre sepa- 

 rates to supply muscle-fibres. 



Two large clusters of nerve- 

 cells have received special names. 

 Kemak's ganglion is a large 

 group of nerve-cells in the wall 

 of the sinus venosus. 



Bidder's ganglion is formed, 

 collectively, by groups of cells in 

 the aurieulo-ventricular groove, 

 the chief groups being attached 

 to the two cardiac nerves. 



No nerve-cells have been dis- 

 covered behind that portion of the ventricle near the aurieulo- 

 ventricular groove, nor has a direct connection between the cells 

 or their processes with the fibres of the pneumogastric nerve been 

 made out. 



Nerve-fibres have been described as existing in all parts of the 

 ventricle and being connected with the muscle-fibres (Openchowsky 

 and others) ; this cannot, as yet, be accepted as proved. 



The truncus arteriosus also possesses nerve-fibres and nerve-cells 

 (Pagliani, Lowit, and others), but their arrangement seems to be 

 very irregular. Lowit did not succeed in finding the nerve-cells in 

 all cases examined ; and Engelmann denies their occurrence.] 



c and d. [The endothelium and connective-tissue of the heart. 



The connective-tissue of the heart exists only in very small 

 quantity. A fine layer on the oiiter surface of the ventricle, 

 especially towards the aurieulo-ventricular groove, can easily be 

 seen (Fig. 138 CT) -, the various valves, the auricular septum, and 

 more particularly the truncus arteriosus, all contain connective- 



Group of nerve-cells on the cardiac nerve, from 

 the auricular septum. Stained with picrocar- 

 mine. Occ. Ill, Syst. 3, Hartnack ; after Dogiel. 

 F Fibres of the cardiac nerve. 

 G Nerve-cells. 



