1 2 8 THE INVOL UNTAR Y NER VO US S YS TEM 



hypogastric. The secretion of the prostate is undoubtedly brought 

 about mainly by secretory fibres in the hypogastric, which, when 

 stimulated, cause a steady continuous secretion, very different from 

 the transitory secretion caused by stimulation of the pelvic nerve. 

 It may, however, be possible that the pelvic nerve also brings 

 about a true secretion and not merely an emptying of the gland 

 by muscular squeezing. These glands at the posterior end of the 

 body may also therefore be derived from the two sources, epi- 

 dermal and endodermal, and thus have a double secretory nerve 

 supply. 



So far we may, I think, draw these conclusions from our 

 present knowledge: (i) the nerve cells which supply secretory 

 nerve fibres to purely epidermal glands, e.g. the sweat glands, 

 all belong to the sympathetic system and are connected with the 

 central nervous system by the thoracico-lumbar outflow of con- 

 nector nerves. (2) The nerve cells which supply secretory fibres 

 to the purely endodermal glands, e.g. gastric and pancreatic, 

 all belong to the enteral system and are connected with the 

 central nervous system by the bulbar (vagus) outflow of connector 

 nerves. 



At the two extremities of the body, where the endoderm and 

 ectoderm come together, the ectodermal and endodermal glands 

 are mixed together and two sets of gland cells may become fused 

 together to form one gland, with the result that that gland is 

 supplied with secretory nerves both from the sympathetic and 

 enteral nervous systems. 



As the result of a consideration of the glandular structures we 

 thus arrive at the same conception of an original double segmen- 

 tation throughout the length of the animal, a somatic and a 

 splanchnic, and we again see that the glands supplied with 

 secretory fibres from the sympathetic system belong to the 

 somatic and not to the splanchnic segmentation, while those 

 wholly supplied by the enteral nervous system are entirely 

 splanchnic. At the extremities of the body where the two 

 systems meet, a fusing of the two types of glandular structure 

 has taken place, which is indicated by a double innervation. 



The third class of glands are those derived from the surface 

 of the coelom and consist of the kidneys. There is at present 

 no evidence that such gland cells are under the control of the 

 nervous system at all. There is evidence that the supply oi 



