( 863 ) 
fluences from without, it stood to reason for me to try whether 
these data were to be used for the identification of blood-spots. 
Now I have first dried some drops of blood from different animals 
(horse, cattle, rabbit) upon small pieces of linen, then extracted 
them by means of salt-solution and injected the extract subcutaneously 
into guineapigs in quantities equal to one drop of blood per animal. 
After the lapse of the usual incubation-stage of 12 ov 14 days or 
longer the animals —- as was indeed to be expected — had become 
hypersensitive to an intraperitoneal injection of 4 or 5 eM.’ of the 
corresponding serum, and that in a quite specifie sense. A guineapig 
e.g@., which has been sensitized with the extract from a cowbloodspot, 
and does not in the least react upon an injection of 5 cM.’ of horse- 
serum, is as sensitive to an injection of the same quantity of cow- 
serum the day after, as a test-animal — likewise sensitized with 
extract from a cowbloodspot — but which previously has not been 
tried with another serum. 
Then 1 have also anaphylactised guineapigs with the extract from 
spots of human blood. Now as for trying these animals in the sub- 
cutaneous or intraperitoneal way rather a great deal of human serum 
would be necessary, I have examined them upon hy persensibility in the 
intracerebral way or by preference by intravenous injection. Thus 
they can very well stand '/, cM.’ of serum from horse, cattle or 
rabbit, but the same quantity of human serum, injected into the 
carotis, kills these animals certainly within a few minutes. 
I am busy continuing this investigation, in the hope of rendering 
the method simpler and more practicable. Meanwhile | have already 
now intended to point out the principle of this method, because | 
think it may perhaps find a place by the side of the well-known 
methods of judicially medicinal investigation of blood. 
Physics. — “Researches on the Jouuw-Krrvin-efject, especially at low 
temperatures. 1. Calculations for hydrogen.” By J. P. DALTON, 
M.A., B.Se., Carnegie Research Fellow. Communication N°, 109¢ 
from the Physical Laboratory, Leiden. 
(Communicated in the meeting of March 27, 1909). 
$ 1. The present calculations form part of a research which was 
undertaken *) with a view to devising an apparatus for determining 
the JouLu-KuLvin-effect obtained in expanding helium at the temperature 
of liquid hydrogen, and thus to lead to some decision regarding the 
1) The beginning of the research was already referred to in Comm. NO, 108 
(Proc. Aug. 1908). 
