Charles Eiissell Bardeen 207 



Of the 14 instances in which the 21st nerve furnished fihres to the 

 rectus muscle, in 9 the vertebral column was apparently normal, and 

 in 5 it was lengthened by an additional vertebra. In 2 instances the 

 plexus was of the normal type, in 10, of the distal type, and in 2 

 instances no good record of the plexus was preserved. See Fig. V. 



No marked relations were noted between these variations in the distal 

 supply of the rectus muscle and sex, race or side of body. Both Huge " 

 and Bolk ' have given interesting accounts of the relations of the distal 

 abdominal and border-nerves in the anthropoid apes. 



The Number of Spinal Neeves Contributing to the Nerve Sup- 

 ply OF THE Abdomen. See Table 77.— In connection with the abdomi- 

 nal nerves it is of interest to inquire how many spinal nerves contribute 

 to the nerve supply of the abdomen. With the possible exception oc 

 twigs furnished by the most distal nerve confined to the thorax to the 

 most anterior portion of the transversalis abdominis muscle, the first 

 nerve of supply of the abdomen is the most anterior intercostal nerve 

 the ventral branch of which passes below the costal margin to enter the 

 abdominal wall. Similarly, with the exception of twigs furnished now 

 and then by the genito-crural nerves, the inguinal nerve is the most 

 posterior nerve furnishing a nerve supply to the abdominal walls. Tak- 

 ing the 1st abdominal nerve as the anterior limit, and the inguinal 

 nerve as the posterior limit, we find that in 10 out of 16 instances 

 (62.5^), seven spinal nerves contributed to the supply of the abdominal 

 wall, in 4 instances (25;^) six nerves, and in 2 instances (12.5;^) five 

 nerves thus contributed. 



The transversalis and internal oblique muscles are supplied by 

 branches which spring from the main abdominal nerves during their 

 course to the rectus, and from the ileo-hypogastric, ileo-inguinal, and 

 sometimes from the genital nerve, during their course between these 

 muscles.- The last nerve also furnishes fibres to the cremaster muscle. 

 The muscular branches springing from these various nerves are irregular 

 in origin and distribution, and give rise to a plexiform union between 

 successive nerve trunks. Owing to the great irregularity of these 

 secondary muscle branches no statistical data concerning them are 

 furnished. 



s T. Ruge : Verschiebungen in den Endgebieten der Nerven des Plexus lumbalis der 

 Primaten. Morph. Jahrbuch X, 1893, p. 305. 



■> Beitrag zur Neurologie der unteren Extremitat der Primaten. Morph. Jahrbuch 

 XXV, 1898, p. 305. 



