474 ANATOMY IN A NUTSHELL. 



tion into the urethra In man they arc small. about the size of a pea, Lying be- 

 neath the membranous portion of the urethra, close behind the bulb and empty- 

 ing into the bulbous portion of the tract. Their size, shape, and position vary 

 in different animals, in some of which they are much more highly developed 

 than in man. 



Tlie tossa navioularis is (a) a recess in the urethra, near the urinary meatus, 

 where the caliber of the tube is enlarged. (1») A depressed space between the 

 posterior commissure of the vulva and the fourchette. 



The lacuna magna is the Largesl of several orifices of mucous follicles, 

 situated on the roof of the fossa naviculars. 



The glands of Littre are the crypts along the spongy portion of the urethra. 



The prostate ("standing in front") is a glandular body situated around the 

 initial portion of the urethra. It develops at puberty, atrophies after castra- 

 tion, and in certain animals increases in size during the breeding season. 



The female urethra is a tube beginning at the meatus urinarius Lnternus 

 in the bladder and ends at the meatus urinarius externus in the vulva. It is 

 about one ami one-half inches long, imbedded in the anterior all of the vagina. 

 perforating the triangular ligament, and surrounded by the fibers of the Com- 

 pressor urethrse muscle. Its diameter is about one-fourth inch, but it is capable 

 of considerable dilatation, being surrounded by softer structures than those 

 around the male urethra. When dilated far beyond its usual calibre it does 

 not lose its tone. 



LESSON CLIII. 



The literal meaning of hernia is branch. It is a tumor formed by the dis- 

 placement and protrusion of a part which has escaped from its natural cavity 

 by some aperture and projects externally. It is sometimes called rupture. 

 We may have hernia of the brain and of the coverings of the cord, of the thorax. 

 or of the abdomen. When we speak of hernia without any qualification, we 

 mean hernia of the abdomen, and this is the most common form, consisting 

 of the protrusion of some part of the viscera through a natural or accidental 

 aperture in the inner wall of the abdomen, the external skin generally remaining 

 unbroken. The following are some of the forms of hernia: 



1. Cerebral hernia, which is a protrusion of the brain through an open- 

 ing in tin' cranial walls. 



2. Ci;i RAL HERNIA or FEMORAL HERNIA is a hernia descending beside the 



femoral vessels. 



'4. Direct inguin \i. hernia is a hernia of the intestine or omentum which 

 descends through the inguinal canal: but uo1 through the internal abdominal 

 ring having broken into the canal below this ring in Hesselbach's triangle. 



4. Tin: [NDIRECT or OBLIQUE [NGl [NAL HERNIA is a hernia whose course 

 is thai of the spermatic cord through the ingiunal canal. 



5. LUMBAR HERNIA is a hernia in the loins or lumbar region. 



6. Phrenic hernia i- a hernia projecting through the Diaphragm into 

 one of the pleural cavities. 



