190 VENOMS 
phenomenon may be that the doses, which are, weak but sufficient 
to produce the disintegration of the leucocytes, injure the red 
corpuscle in only a slight degree, while the stronger doses are 
equally destructive to the two kinds of blood corpuscles. 
It follows that we must understand that there are two phases 
in the action of venoms: one negative, when the dose absorbed 
does not injure the leucocytes ; the other positive, when the leuco- 
cytes are destroyed. 
If the blood of the dog remains non-coagulable when mixed 
with doses of venom which, on the contrary, are actively coagulant 
for the blood of the rabbit, the reason would be that the leucocytes 
of these animals are not equally resistant to venom. 
This conception, however, does not conform to the facts that 
I have myself observed. I have always found that viper-venom, 
mixed with citrate- or oxalate-plasma of the dog, rabbit, or horse, 
coagulates these various plasmas when the venom is in weak doses, 
while with strong doses coagulation is not produced. To be quite 
accurate, 1t should be stated that the quantity of venom necessary 
to render the plasma of the dog, or of the horse, non-coagulable 
is less than that which must be employed in the case of the plasma 
of the rabbit. 
I have caused Noc to take up anew the study of this question 
in my laboratory, with venoms of nine different origins, and 
I here give a résumé of the results of his researches.' 
I. COAGULANT VENOMS. 
The venoms of VIPERID® studied range themselves as follows 
according to their coagulant power :— 
Croratinaz: Lachesis lanceolatus (Fer-de-lance, Martinique). 
Lachesis neuwiedii (Urutu, Brazil). 
Lachesis mutus (Bushmaster, or Surucucu, Brazil). 
Lachesis flavoviridis (Japan). 
VIPERINÆ : Vipera russellii (Daboia, India). 
1 Annales de l'Institut Pasteur, June, 1904, 
