THE RHYTHMIC AND PERISTALTIC MOVEMENTS 113 



fibres from two sources belonging to the vagus and sympathetic 

 systems respectively, each of which influences the nerve cell 

 apparatus in the organs themselves. They do not it seems to me 

 lay any importance on the difference of these two connexions ; 

 the nerve fibres of the one being pre-ganglionic or connector 

 fibres with a medullated, sheath and of the other post-ganglionic 

 and usually non-medullated fibres. They see no difficulty in the 

 view that the non-medullated accelerator and augmentor fibres of 

 the heart or the non-medullated inhibitory fibres of the intestinal 

 muscles should make connexions with another group of sympa- 

 thetic cells within the heart and intestine respectively before 

 reaching the muscular tissue. 



The chief exponent of this view is Dogiel, and it is based 

 mainly on histological evidence obtained largely by the ap- 

 pearances after staining the living tissue with methylene blue. 

 In the case of the intrinsic nervous apparatus of the intestine 

 of mammals, Dogiel finds in Auerbach's plexus two main types 

 of nerve cells, which he designates as cells of Type I and Type II 

 respectively. He speaks throughout of the cells of Type I as 

 motor cells of the sympathetic system. Dogiel gives a history of 

 the investigation upon the nature of Auerbach's plexus before 

 his own, and points out that Ramon y Cajal in 1893 investigated 

 Auerbach's plexus by his modified Golgi method, and came to the 

 conclusion that the cells of the ganglia are multipolar and pos- 

 sess three to eight processes, which can be followed for a long 

 distance. He considers these processes to be nervous and to. 

 form complicated plexuses round the muscular and glandular 

 structures. The fibres which simply pass through the ganglia he 

 considers to be non-medullated and to arise probably from sym- 

 pathetic ganglia outside the intestine. In addition there are 

 fibres which form arborizations round the cells, but he does not 

 know where they come from. After Dogiel had described his 

 two types of cells, la Villa, a student of Cajal, re-investigated and 

 found Dogiel's Type I which had been missed by Cajal, because 

 it was so much more difficult to stain than Type II. Cajal's 

 description therefore refers to Type II exclusively. 



In the course of the investigations into the structure of 

 Ammoccetes, which Miss Alcock has carried on through so many 

 years, she has found in the intestine groups of nerve cells of an 

 ordinary description, perfectly visible without any special staining 



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