CAVERNOUS VESSELS. VASCULAR PLEXUSES. 293 



round or slightly polygonal cells, replaced in recently born 

 animals by true ciliated epithelium. The rich supply of 

 nerves to these supposed glands, and especially of sympathetic 

 fibres, and their position near the lower extremity of the great 

 sympathetic, appears to justify the view that whilst the hypo- 

 physis is the cerebral pole of the sympathetic, this gland con- 

 stitutes the anal pole, and is to be regarded as a nervous gland. 



Luschka's statements, so far as regards the presence of gland 

 vesicles and tubes, have recently been corroborated by Krause * 

 Arnold,*!" however, calls the glandular structure of this organ 

 in question, pointing out that the glandular bodies of the mid- 

 dle sacral arteries are capable of being injected, and that they 

 only represent ampullar and fusiform dilatations of the lateral 

 and terminal branches of that artery ; in other words, a true 

 plexus arteriosi coccygei. 



These vascular sacculi, which may already be found as small, 

 partial, but true aneurisms in the course of the middle sacral 

 artery, and in larger number enter into the composition of the 

 coccygeal gland, consist, according to Arnold, of an investment 

 of connective tissue, which covers a layer of concentrically 

 arranged and obliquely coursing muscular fibres, within which 

 again is a delicate structureless coat, resembling the elastic 

 fenestrated membrane. The innermost layer, the epithelial- 

 like coat of the gland vesicles and tubes of Luschka, is com- 

 posed of fusiform and polygonal cells, which frequently overlap 

 each other at their edges. The connective intervening sub- 

 stance of this is rich in muscles, which run in the most diverse 

 directions, and form a continuous layer on the surface. 



At a later period Arnold discovered the existence of similar 

 structures, consisting partly of vascular sacs, and partly of 

 retia mirabilia, in the course of the middle sacral artery in the 

 dog, cat, otter, squirrel, rabbit, rat, horse, ox, and pig. 



Krause and MeyerJ have therefore corroborated the princi- 



* Zeitschriftftir rationelle Medicin, Band x., 3 R., p. 293. Anatomtsche 

 Untersuclnmyen. Hannover, 1860, p. 98. 



t ArcMvfur Pathologische Anatomic, xxxii., p. 293, 1865; xxxv.,p.454, 

 1866 ; xxxix., p. 220, 1867. 



t Zeitschrift fur rationelle Mcdicin, xxviii. 



