25 
the vaso-constrictor muscle as to render small doses of adrenalin 
ineffective. So it may not be far wrong to attribute the loss of sensi- 
tiveness to small doses of adrenalin in cats and rabbits to a loss of 
irritability in the more advanced stages of chloral or paraldehyde 
anesthesia instead of to so-called acquired immunity (tolerance) . May 
not Cushny’s results with rabbits have been of this nature Hunt not 
only observed no loss of irritability toward small doses of adrenalin 
but secured with rabbits some of his best results. 
After trying different anesthetics it was found that ether on the 
whole was the most satisfactory, and so it was used in all of my later 
experiments. As is well known the chief objection to this anesthetic 
is the difficulty of maintaining a uniform condition of anesthesia. 
But this is practically removed by using a modification of the drop 
method suggested by Porter. In this wny even cats, proverbial for 
their vasomotor ‘‘storms,’’ yielded results that were very consistent. 
On the wffiole I prefer morphine along wdth ether for dogs and ether 
alone for cats. Mffien wnrking wdth small doses of adrenalin the 
best results are assured by an anesthesia just sufficient to maintain 
a condition of unconsciousness so that the animal has no pain, wdth 
only enough curare to render it free from muscle tremors. The 
amount of curare given must of course be determined by experience, 
since not only different samples vary but individual animals also 
vary to a certain extent in their reaction to this drug. Indeed large 
doses of curare should be avoided. Being a depressant, it lowers 
the blood pressure and interferes wdth the action of adrenalin, often 
making consistent results impossible, even with dogs, wdiich in my 
experience yield the most reliable results.® 
In all the later experiments the injections wwe made from a 
standardized 1 c. c. syringe graduated in five-hundredths of a c. c. 
The cannulse w^ere of small bore, provided with very short connec- 
tions allowing a minimum amount of dead space. There was one 
injection set for each of the tw’o solutions to be compared so that one 
solution might be injected into the right and the other into the left 
saphenous vein. When constant results w^ere thus obtained the 
solution formerly used for the left vein was now injected as a check 
into the right vein from the right injection set and vice versa. 
The following blood-pressure tables are results selected as typical 
from 21 animals (cats and dogs). Tables I to VI inclusive represent 
in a general w^ay the relative physiological activity of synthetic 
dl-adrenalin and natural 1-adrenahn. The latter of these compounds 
has already been described. The synthetic dl-adrenalin manufactured 
“This animal even at the end of a nine-hour experiment yielded with 1 c. c. injec- 
tions of a 1:100,000 adrenalin solution a rise of blood pressure equivalent to that from 
the first injections of this amount, showing in no case a diminished sensitiveness to 
1-natural and dl-synthetic adrenalin unless too much ether was administered. 
