208 SPECIAL HISTOLOGY. 



size as those of the pelvis of the kidney, to which irregularity 

 the numerous depressions of various depths on the under 

 surface of the uppermost cells, for the reception of the ends of 

 the deeper, elongated cells, much contribute; peculiar stellate 

 and dentate forms being thence produced. In the neck of the 

 bladder and towards the fundus, there occur minute glands, in 

 the form of simple pyriform follicles or small aggregations of 

 these (simple racemose glands). These glands, 0*04 — 024"' in 

 size, have orifices of 0*02 — O05"' ', a cylindrical epithelium, and 

 contain a clear mucus. In pathological conditions, as Virchow 

 informs me, they are occasionally enlarged and filled with 

 whitish mucous plugs. 



The male urethra will be described with the sexual organs. 

 That of the female presents a reddish mucous membrane with 

 numerous vessels, especially in the form of much developed 

 venous plexuses in the submucous tissue (which Kobelt, without 

 any reason, has described as a corpus spongiosum) , and a squamous 

 epithelium, the deeper-seated cells of which are elongated, as 

 in the bladder. There is an external muscular tunic united with 

 the mucous membrane, consisting of a thin layer of longitudinal 

 and transverse smooth muscles, intermixed with much connec- 

 tive tissue and elastic fibres, and of the thick substance of the 

 musculus urethralis, the direction of the fibres in which is 

 chiefly transverse. A certain number of larger and smaller 

 racemose mucous glandules (" glands of Littre"), resembling 

 in their structure those of the bladder, except that they are 

 usually somewhat larger and more closely placed, pour their 

 secretion into the urethra. Occasionally these glands occur of 

 larger size (as much as 2'"), and prominent, containing a 

 colloid-like material in the distended vesicles. 



§191. 



Physiological remarks. Development of the urinary organs. 

 — According to Kemak, the kidneys, in the Chicken, are formed 

 as two protrusions of the intestine, in the constitution of which 

 the epithelial and the fibrous layers both take part, and, like 

 the luugs, grow by the ramification of their epithelial tube, 

 and the augmentation in bulk of the fibrous layer (Unters. z. 

 Entw. d. Wirbelth. Tab. II, fig. 83-85). In the Mammalia, the 

 earliest stage of the development of the kidneys has not yet been 



