318 ON THE INTRODUCTION OF AIR INTO THE VEINS. 
and the circulation become embarrassed : they are both of them 
accelerated—the strength of the animal diminishes, and consi¬ 
derable anxiety and agitation are manifested . 
If, after the development of these disturbances, we stop the 
experiment, most of the animals presently experience very de¬ 
cided relief, and, by degrees, every unpleasant symptom com¬ 
pletely passes away : or, if some are lost, it is less from the in¬ 
troduction of the air than from some accidental disease. 
If, however, the introduction of the air is continued, the re¬ 
spiration becomes more and more laborious—the debility is 
extreme—the animals void their urine and faeces, convulsions 
succeed, and death is not far off. 
The rapidity with which death succeeds depends on various 
circumstances, such as the degree of vital power, and of resist¬ 
ance to these attacks upon it—the size and species of the 
animal—his state of health prior to the experiment—the position 
in which he was placed—the quality of the air, the quantity of 
it which entered the vein, and the quickness with which the 
introduction of it was effected. We subjoin a few illustrations 
of these. 
1. Period of death after the admission of the air into the vein. 
A, Dogs placed in a horizontal position. 
a. Not weakened before the experiment. 
In five of these animals three did not die in consequence of 
the admission of air into the veins. One died on the fifth day 
of accidental pleuro-pneumonia. The second dog lived four days 
after the experiment. The third was destroyed ten minutes after¬ 
wards ; but so little affected by the experiment did he seem to be, 
that he probably would have lived many days, or, perhaps, alto¬ 
gether recovered. One of the other two died in a quarter of an 
hour, seemingly from the closing of the orifice of the vein through 
which the air had been introduced. The last of the five lived 
half an hour after the experiment. 
h. Dogs enfeebled or ill before the experiment. 
Five dogs were subjected to this experiment. Three of them 
died immediately on the introduction of the air. Of the other 
two, one died in four and a half minutes, and the other in twenty- 
five minutes. 
These and some other experiments seem to prove that, all other 
things being the «ame, death sooner occurs in those that have 
been previously enfeebled than in others that retain their full 
strength. 
B, Dogs placed in a vertical position. 
a. Dogs not weakened before the experiment. 
Of four dogs thus placed one only lived four days, and was 
