70 
ileum. The needle is introduced its whole length (1.25 inch) strictly 
subcutaneously toward the middle line. This part of the operation 
is arranged so that the point of the needle will be just about at the 
linea alba. 
It is of the greatest importance to keep the needle out of the peri- 
toneal cayity, and care must also be exercised not to pierce the skin 
too superficially, and it is essential to keep out of the muscles. 
Probably no part of the entire procedure is more important than 
the inoculation of the toxine and antitoxin into the proper tissue of 
the guinea pig. By always injecting the toxine into the same tissues 
we insure three factors: (1) The rate of absorption, (2) the pressure 
effects are relatiyely the same in the same anatomical structures, and (3) 
the relation between the toxine and the receptors of the cells and body 
juices is comparatiyely constant when the injection is made into the same 
anatomical structures. If any of the toxine enters the peritoneal 
cavit}" the rapid absorption may result in the untimely death of the pig 
with an extensiye hemorrhagic reaction. 
Still greater care must be exercised to keep the toxine out of the 
muscles. This point was brought out by Ehrlich and has since been 
emphasized by S. J. Meltzer" and John Auer in their work “On 
the rate of absorption from intramuscular tissue," with curare and 
adrenalin. 
It has been shown that the rate of absorption from muscular tissue 
is so actiye that poisons injected into the muscles are apparent!}^ two 
and three times as strong as when injected into the subcutaneous tissue. 
Ehrlich selects for the site of injection the skin at the median line 
in the region of the xiphoid process of the sternum, and is careful to 
insert the needle purely subcutaneously by pinching up the skin 
which is loose in this region. 
For the purposes of determining at autopsy the exact site at which 
the toxine and antitoxin mixtures haye been inoculated, little particles 
of burnt cork are used by Ehrlich. In this laboratory we use a little 
sterilized powdered animal charcoal, simply for its conyenience. 
Upon dissection the particles of carbon ma}^ plainly be seen and 
show the place where the fluid was injected. This technique has its 
particlar yalue in determining the dose. 
^^'e haye found that if the fluid enters the proper abdominal layer 
it produces an egg-shaped swelling parallel to and oyerlying the linea 
alba. 
As soon as the toxine-antitoxin mixture is injected into the animal 
the rubber bulb is remoyed and an assistant adds the necessary amount 
of salt solution to make up the I c. c. which, after washing down the 
«!Meltzer & Auer: On the rate of absorption from intramuscular tissue. Am. med. 
(abstract), v. 9 (102), Jan. 14, 1905, p. 75. 
