THE URINARY ORGANS. 2O3 



the ureter and the bladder are largely composed of sympathetic fila- 

 ments comprising both medullated and non-medullated fibres. The 

 fibres pass into the mucosa as far as the epithelium ; but whether 

 they penetrate between the epithelial cells is still undetermined. 

 Numbers of microscopic ganglia are situated along the course of 

 the nerves of the bladder, this organ affording in smaller animals a 

 favorable situation for studying ganglion-cells and nerve-fibres, as 

 well as involuntary muscle cells. 



THE URETHRA. 



The urethra, both male and female, consists of a mucous coat, 

 strengthened by a variable muscular tunic and by fibrous tissue. 



The female urethra is lined throughout by a stratified squa-j / 

 mous epithelium, which rests upon a basement-membrane cover-i /" 

 ing the numerous small papillae with which the surface of the tunica 

 propria is beset. These papillae are especially plentiful and well 

 developed near the termination of the canal, in the vicinity of the 

 meatus. The tunica propria, or stroma of the mucosa, is composed 

 of interwoven bundles of fibrous and elastic fibres, the superficial 

 layers of which, particularly in the vicinity of the internal orifice, are 

 infiltrated with lymphoid cells. Small acinous glands are sparingly 

 present. The muscular tunic is well developed and arranged 

 as an inner longitudinal and an outer circular layer of non- 

 striped muscle. The intermuscular connective-tissue lamellae contain 

 many elastic fibres. 



The male urethra is lined with epithelium, the character of which 

 varies in the different portions of the canal. In the prostatic part 

 the epithelium resembles that lining the bladder, being of the transi- 

 tional variety ; this passes gradually into the stratified columnar 

 type of the investment of the membranous part, which in turn 

 gives place to a single layer of simple columnar cells in the penile 

 portion. The fossa navicularis is lined with stratified squamous 

 epithelium continuous with that covering the glans. The tunica 

 propria bears numerous papillae, which are particularly well devel- 

 oped within the navicular fossa. The small racemose glands of 

 Littre are found through the entire urethra. Inner longitudinal 

 and outer circular bundles of non-striped muscle surround the pros- 

 tatic portion, extending over the membranous part to be lost on the 

 spongy. In addition, the fibres of the compressor urethras muscle 

 contribute a distinct muscular investment for the membranous por- 

 tion, which fades away at either border over the penile and prostatic 

 segments. The anterior part of the penile division is destitute of 

 muscular tissue. Outside of the muscular layer a variable fibrous 

 tunic gives additional firmness and strength to the canal. The walls 



