Diptera 
35 
solution. The drop was allowed to dry, it being thought that the 
salt crystals would facilitate the grinding up of the glands with the 
end of a small glass rod, this being done under microscopic control. 
After grinding up, a small drop of water was added of the size of the 
original drop of saline, and an equal volume of human blood taken 
from the clean finger-tip was quickly mixed therewith, and the whole 
drawn up into a capillary tube. Clotting was not prevented and no 
hemolysis occurred. Salivary gland emulsion added to a dilute 
suspension of corpuscles did not lead to hemolysis. This experi¬ 
ment was repeated a number of times, with slight modification, but 
with similar results. The data obtained from the series “do not 
support the hypothesis that the salivary glands, at any rate in Culex 
pipiens, contain a substance which prevents coagulation.” 
Much more detailed, and the more important experiments made 
along this line, are those of Schaudinn (1904). The results of these 
experiments w^ere published in connection with a technical paper 
on the alternation of generations and of hosts in Trypanosoma and 
Spirochoeta, and for this reason seem to have largely escaped the notice 
of entomologists. They are so suggestive that w r e shall refer to them 
in some detail. 
Schaudinn observed that the three oesophageal diverticula (com¬ 
monly, but incorrectly, knowm as the “sucking stomach”) (fig. 24) 
usually contain large bubbles of gas and in addition, he always found 
yeast cells. On the ground of numerous observations, Schaudinn 
was convinced that these yeast plants are normal and constant 
commensals of the insect. He regarded them as the cause of the gas 
bubbles to be found in diverticula. It was found that as the insect 
fed, from time to time the abdomen underwent convulsive contrac¬ 
tions which resulted in the emptying of the oesophageal diverticula and 
the salivary glands through blood pressure. 
In order to test the supposed toxic action of the salivary glands, 
Schaudinn repeatedly introduced them under his skin and that of 
his assistant, in a drop of salt solution, and never obtained a sugges¬ 
tion of the irritation following a bite of the insect, even though the 
glands were carefully rubbed to fragments after their implantation. 
Like Nuttall, he failed to get satisfactory evidence that the secre¬ 
tion of the salivary glands retarded coagulation of the blood. 
He then carefully removed the oesophageal diverticula with their 
content of yeast and introduced them into an opening in the skin 
of the hand. Within a few seconds there was noticeable the charac- 
