Electro-physiology and electro-therapeutics : showing the best methods for the medical uses of electricity / By Alfred C. Garratt.

As each dorsal nerve root escapes from its inter-vertebral foramen in a downward and outward direction, the trunk immediately divides into two main branches, much as we have seen in the eight above ; the one is called the dorsal or back branch, while the other constitutes the true intercostal nerve. The short posterior dorsal branches pass directly out backward, first distributing to the back muscles, and even to the deep erector spina; they then terminate profusely in the integument of this middle portion of the back, and even in the integument of the lumbar region in and near the middle line ; so also some external brandies are distributed to the skin and fascia upon the sides of the lumbar and gluteal region. The twelve intercostal nerves, after receiving a filament each from the adjoining ganglia of the sympathetic, pass separately forward, running along in the intercostal spaces between the ribs, supplying the muscles as they pass, some terminating at the anterior termination of the intercostal space near the sternum; at this point the longer branches pierce the intercostal and pectoral muscles, then turning more down- ward and outward, are distributed to the integument of the mamma, and over the front of the chest. Those lower down, which are situated between the false ribs, pass behind the costal cartilages, and then outward between the muscles trans- versalis and the obliquus interims, then supplying the rectus abdominis muscle, and the integuments over the front of the abdomen. The first and last dorsal nerves come short of all this distribution. The branches of each intercostal nerve are, first, a muscular branch, (which has no cutaneous twigs;) and, second, a cutaneous branch, which is given off to become super- ficial at about the middle of the arch of each of the ribs. The cutaneous branches of the upper three intercostal nerves are not distributed on the body, but rise to radiate on the back of the upper arm, and hence are called the intercosto-lmmeral nerves. One of these is of a large size, and is widely distributed over the integuments of the back and inner aspect of the upper arm, as far down as the elbow. Another smaller branch is distributed to the integument of the extreme tip of the shoulder. One