382 



The Popliteal Nerves 



the outer side of the dorsalis pedis artery, to the cleft between the 

 great toe and the next, whilst the outer branch ends in a ganglionic 

 thickening beneath the short extensor of the toes, which muscle it 

 supplies. Its other muscular branches are to the tibialis anticus, 

 extensor proprius hallucis, extensor longus digitorum, and to the con- 

 tinuation of the last muscle, the peroneus tertius. 



When there is paralysis of the external popliteal nerve the patient 

 cannot flex or evert the foot, nor extend the toes. The foot remains 

 in the position of inversion and extension, the toes being curled towards 

 the sole ; as the patient walks the toes catch against the ground, 

 and progression is rendered difficult and dangerous. When there has 

 been complete section of the nerve, as may happen after careless 

 tenotomy of the biceps, sensation is impaired on the outer aspect of 

 the leg and the dorsum of the foot ; and, on account of the implication 

 of the trophic filaments, sores may occur in the skin of those neigh- 

 bourhoods. 



THE RECTUM 



This last part of the large intestine is by no means 'straight.' It 

 begins opposite the left sacro-iliac joint, and inclines to the middle of 

 the sacrum (first piece) ; then it follows the curvature of the sacrum 

 and coccyx (second piece), and afterwards it bends backwards for 

 \\ in. between the levatores ani, to end at the level of the external 

 sphincter (third piece). It measures about 8 or 9 in., and 'is capable 

 of enormous distension. 



The curves taken by the rectum must be specially remembered in 

 the introduction of an enema-tube or bougie. An ignorant and clumsy 

 operator pushing an enema syringe directly upwards might injure the 

 prostate or the recto-vaginal septum, and entirely fail to irrigate the 

 bowel. And in the case of imperforate rectum, when the bowel is 

 being sought through the perineum, the dissection must be carried 

 well back along the sacro-coccygeal curve. In the young child, how- 

 ever, the rectum runs a comparatively straight course. 



Though not properly a reservoir for fteces, the rectum is in some 

 cases accustomed to contain a large amount of accumulation, us is 

 often made out during digital exploration. In the healthy condition 

 of the bowel the presence offices is a stimulus to the muscular wall 

 to contract. But in the subject of habitual constipation the nerves 

 and muscle become degenerate, and cease to act. The scnsitivciu-ss 

 of the lining of the rectum is very slight at a little distance above the 

 inner sphincter, and thus it happens that the bowel may be over- 

 loaded with forces without the patient being in discomfort. In such a 

 case a doughy tumour may be found in the left lumbar and iliac 

 regions. The pressure thus exerted upon the iliac veins may cause 

 ia oi the left thigh and leg. The more diluted the bowel, the 



