234 CLINICAL APPLIED ANATOMY. 



disease. A true neuritis may also occur. Sometimes neuritis 

 is a manifestation of a general toxaemia of pregnancy, sometimes 

 it is due to the local extension of pelvic inflammation, for the 

 plexus lies in the planes of pelvic connective tissue. 



The most interesting lesion from an anatomical point of view 

 is a sudden paralysis which may come on during childbirth. 

 The paralysis is attributed to pressure by the foetal head on its 

 passage through the pelvis. The muscles supplied by the 

 peroneal nerve are usually affected. The peroneal nerve is 

 derived from the dorsal divisions of the lumbo-sacral cord, and 

 the first and second sacral nerves. The dorsal constituents of 

 the lumbo-sacral cord lie next to the bone as the cord passes 

 over the true pelvic brim and so are exposed to pressure, whereas 

 the lower roots of the sacral plexus lie on the pyriformis muscle, 

 which affords some protection. The gluteal nerves are some- 

 times involved at the same time as the peroneal ; these nerves 

 are also derived from the dorsal divisions of the lumbo-sacral 

 cord and first and second sacral nerves. 



INJUEIES TO THE PEKIPHERAL NERVES OF THE LIMBS. 



Division of the peripheral nerves of the extremities is a common 

 lesion, especially in the upper limb. Hence a thorough know- 

 ledge of the distribution of these nervous trunks is of great 

 practical importance. Injury may be the result of accident or 

 operation. 



The Upper Extremity. The chief nerves that may be damaged 

 are the ulnar, the median and the rnusculo -spiral. 



The ulnar nerve arising from the inner cord of the brachial 

 plexus runs along the inner side of the arm, and enters the fore- 

 arm in the space between the internal epicondyle of the humerus 

 and the olecranon process of the ulna, in which position it is 

 liable to injury in fracture of the condyle, in excision of the elbow 

 joint and in punctured wounds. Passing between the two heads 

 of the flexor carpi ulnaris, it pursues a course down the ulnar 

 side of the forearm under cover of this muscle, and at the wrist, 

 lying on the radial side of the pisiform bone, it enters the palm 



