HuBER, Sympathetic Nervous System. 99 



clearly seen in double stained preparations, only the nerve fiber 

 staining blue, the muscle cell red. This is especially well shown 

 where a heart muscle cell and ending are cut transversely ; in 

 such a case it may be seen that the ending rests on the cell and 

 does not in the least enter it. The more complex endings de- 

 scribed correspond, I think, to the end-apparatus of the second 

 type mentioned by Berkley (46). In preparations made of the 

 auricles of a cat's heart, I find no appearances which might lead 

 me to think that nerves having a distinctive structure are asso- 

 ciated with characteristic endings as Berkley (46) has stated in 

 the admirable account from which the quotations above given 

 were taken. In the cat, nerve fibers going to the more simple 

 and the more complex endings are distinctly varicosed, and fur- 

 thermore the endings seen by me vary so in complexity, from a 

 single small end bulb, to one with two, three, four or more nodular 

 enlargements, that a division into two types would be a purely 

 artificial one. In my preparations I have found no bulbous en- 

 largements, which might be interpreted as bipolar cells, such as 

 Berkley (46) has described. I have however often found large 

 sheath-nuclei on the non-medullated fibers, plainly made out in 

 double stained preparations, which, if stained with the nerve 

 fiber after the Golgi, method, might, I believe, give an appearance 

 similar to the bulbous enlargement described by Berkley. 

 While not denying the existence of bipolar cells in the heart, it 

 would seem that further confirmatory observation is necessary 

 before their presence is assured, and that with methods by means 

 of which the structure of these nodules may be ascertained. 



To summarize this portion of my subject, I may say that 

 the neuraxis of sympathetic neurons (most probably those in 

 the heart ganglia) terminate on the heart muscle cells either by 

 *a very simple ending, one that resembles those found in invol- 

 untary smooth muscle, or by a more complicated ending, resem- 

 bling slightly the ending in striated muscle. The question may 

 here be asked — do all heart muscle cells have a direct innerva. 

 tion? As already stated, Heymans (49) suggests this for the 

 frog's heart. In well stained preparations of the auricle of a 

 cat's heart it would appear from the number of nerve fibers 



