208 Study of the Abdominal and Border-Nerves in Man 



The lateral branches of the intercostal nerves furnish nerves to the 

 external oblique muscle and cutaneous branches which vary much in 

 distribution. I have seen, for instance, a combined nerve trunk, arising 

 from the lateral branches of the 11th and 13th thoracic nerves, extend 

 well into the pubic region. The charts furnish, however, insufficient 

 data on which to base a statistical study of variations in the lateral 

 cutaneous branches of the eleven more anterior intercostal nerves. On 

 page 310 the relation of the lateral branch of the 13th intercostal nerve 

 to the iliac region is considered. 



The Vaeious Types of Disteibution of the Boeder-Neeves. See 

 Table V, and Figs. 1-8. — Greater variation seems to exist in the origin 

 of the border-nerves from spinal nerves than in the origin of the main 

 abdominal nerves. With the exception of the genito-crurab nerves, how- 

 ever, the courses taken by the border-nerves are fairly definite and are 

 well described in the standard text-books. We shall consider first the 

 variation in origin of the border-nerves taken as a group, and then that 

 of the individual border-nerves. 



In Tal)le V, we have divided the sets of border-nerves found in the 

 subjects studied into various types. The five main types are based upon 

 the spinal nerves from Avhich the border-nerves arise. In Type I, all 

 border-nerves arise from the 30th and 31st spinal nerves; in Type II, 

 from the 31st; in Type III, from the 30tli, 31st and 32nd; in Type IV, 

 from the 31st and 33nd; and in Type V, from the (30), 21st, 23nd and 

 23rd. Types I, III and IV are further subdivided into sub-types, ac- 

 cording to the relation of the spinal nerves to the individual border- 

 nerves. These relations are made clear by the table. It will be noted 

 that the border-nerves most frequently arise from the 30th, 31st and 

 33nd spinal nerves, and next most frequently from the 31st and 33nd. 

 Types III and IV A., the forms most commonly met with, correspond 

 with the pictures given in most text-books to illustrate the normal type. 



Kelations of Race, Sex and Side of Body to the Various Types 

 OF Distribution of the Bordee-Nerves. See Table VI. — In Table 

 VI are given the relation of race, sex and side of body to the various 

 types of distribution of the border-nerves. It will be noted that no very 

 marked relations of this nature seem to exist. A much larger number 

 of instances than we have studied would be necessary before reliable 

 deductions could be drawn as to the influence of these factors in determ- 

 ining variation in the distribution of the peripheral nerves under dis- 

 cussion. 



