218 CLINICAL APPLIED ANATOMY. 



groups. These groups are most numerous in the cervical and 

 lumbar enlargements and extend in a vertical direction through 

 a varying number of cord segments, some extending through as 

 many as three or four whilst others are limited to one. It is 

 assumed that each cell group represents a particular muscle. 

 If the cell group is entirely destroyed the muscle is completely 

 paralysed, whilst partial destruction, which is more likely to occur 

 when the cell group extends through several segments, leads to 

 paralysis of part of the muscle only. 



Several types of infantile paralysis may be recognised, depend- 

 ing upon the position occupied by the spinal lesion. 



In the leg type the peroneal and the anterior tibial groups 

 of muscles are involved, occasionally the posterior tibial group, 

 including the calf muscles, as well. Keference to the table 

 of muscular representation in the cord, indicates that the 

 lesion in such cases is in the lower lumbar and sacral regions. 

 The functions of the bladder and rectum may be interfered with 

 owing to the proximity of the centres for these organs. The 

 resulting deformities affect the ankle and foot. Owing to the 

 continued unopposed activity of the calf muscles talipes equinus 

 may be produced. When paralysis preponderates in the peronei, 

 the foot becomes inturned, and talipes varus occurs, because of 

 the unopposed action of the anterior tibial group. 



In the thigh type of paralysis the iliacus, psoas, quadriceps 

 extensor and glutei suffer, the adductors often escaping. The 

 lumbar region of the cord is the site of the lesion in such cases. 

 Owing to the unopposed action and ultimate contracture of 

 the hamstrings, the knee may become fixed in a position of 

 flexion. The head of the femur may fall from its proper 

 position in the acetabulum, and even become further displaced. 

 Paralysis limited to the muscles of the thigh produces serious 

 disability owing to the position of the paralysed segment at the 

 junction of the trunk and lower limb. Under these circum- 

 stances the part of limb below the knee is practically useless 

 although its muscles are intact. 



The arm may be paralysed in either its upper or lower 



