DEVELOPMENT OF THE RECTUM 13 



anal orifice, and which open by small ducts on the skin just lateral 

 to the anus. He also describes 'sudoriparous' glands which 

 apparently include both Herrmann's intramuscular glands and 

 Zimmermann's 'circum-anal' glands. He also describes the 

 close relation of the lymphoid nodules to the anal mucous mem- 

 brane of the dog, and remarkis upon their close resemblance to the 

 structure of the tonsils. With regard to this he says: '' N'y a-t-il 

 pas lieu ainsi d'admettre, de la part des glandes anales par les 

 follicules clos qu'elles renferment, une action analogue a cette 

 jouee par les amygdales a I'autre porte d'entree du tube digestif?" 



Zimmermann ('04) has made a careful and complete stud}^ of 

 the glands of the anal region of the dog. He divides the anal 

 mucous membrane into three zones: the zona cutanea, which is 

 composed of internal and external subdivisions, the zona inter- 

 media, and the zona columnaris. All these regions are lined by 

 a stratified squamous epithelium, which takes on more and more 

 the structure of the skin when passing downward from one region 

 into the next. The zona columnaris is characterized by columns, 

 sinuses and valves. The sinuses are not always equally well 

 formed and some 'Sinuositiiten' extend in the form of branched 

 canals or crypts into the region of the lymphoid nodules. These 

 structures, he speaks of as the 'anal tonsils.' The zona inter- 

 media is characterized by its smooth epithelium and the ducts of 

 the large 'reservoir glands.' The zona cutanea takes on more and 

 more the structure of the skin when followed downward. The 

 internal portion lies within the anal canal, the external without. 

 This zone contains large sebaceous glands (which according to 

 Zimmermann have incorrectly been called 'circum-anal glands') 

 and sweat glands, both of which open into hair infundibuli in 

 which hair shafts are lacking. 



For an account of the anal regions of the domestic animals, the 

 reader is referred to the work of Mladenowitsch ('07) who has 

 studied this portion of the rectum of the horse, ox, sheep, goat, 

 pig, dog, and cat. He finds that the columns of Morgagni, or 

 rectal columns, and the rectal sinuses are constant structures. 

 Blackman ('11) is referred to for an account of the anal glands of 

 the skunk. 



