344 Annals Entomological Society of America |Vol. VIII, 
mammals being only shghtly or not at all affected. Thus the 
red blood corpuscles of the rabbit and rat are very sensitive 
to the poison of the house-spider (‘‘Kreuzspinne,’’ Araneus 
diadematus Clerck) and undergo complete haemolysis, those 
of the mouse, man and goose are less sensitive and in the case 
of the guinea pig, horse, sheep and dog even great quantities 
of the poison do not produce hemolysis.* It is this peculiar 
property of the poisons, known as hemolysis, that I have begun 
to investigate in plant lice. My work has been carried on 
with an unidentified species of plant-louse living on Pelargonium, 
the hemolytic experiments being performed in the traditional 
manner.j Among the animals investigated the red blood 
corpuscles of the ox were found to be sensitive to the poisons 
of the plant-louse. 
The plant dice were triturated 1m ‘a (certain: quantitymer 
physiological salt solution (0.8 per cent) or in a mixture of 
glycerine and physiological salt-solution and placed for 24 
hours in the. ice-chest. Then, after filtration, the extract 
was used. On the other hand, I obtained a solution of defibri- 
nated ox blood, drawn off under aseptic conditions, of 5 per cent 
solution. This was centrifuged, the liquid being thrice replaced 
with physiological salt solution, which finally gave a 5 per cent 
dilution of red-blood corpuscles. This dilution was mixed in 
variable quantities with plant-louse extract in small tubes, 
such as are used for serum investigations. Then the tubes 
were warmed in the thermostat for two hours at 37°C. and 
placed over night in the ice-chest to obtain the sedimentation 
of such blood-corpuscles as were not dissolved. At the same 
time control experiments were carried on in such a manner 
that the control tubes were heated and placed in the ice-chest 
together with the tubes containing the extract. In these control 
experiments the plant louse extract was replaced by a cor- 
responding amount of the physiological salt-solution or of a 
mixture of physiological salt-solution and glycerine. 
It was found that the warm dilutions of the extract hamolyze 
the blood-corpuscles of the ox and that this ‘‘hemolysis’’ 
*Hans Sachs, Zur Kenntnis des Kreuzspinnengiftes. Beitr. Chem. Physiol. 
u. Pathol. (Hofmeister) Bd. 2, 1902, pp. 125-133. 
jUnfortunately, I am unable at the moment to give the scientific name of 
this plant-louse. 
