SNAKE-POISON LITERATURE. 



71 



Morsu virus habent, et fatum dente minantur 



Pocula morte carent." 



Fontana's criticisms of the different theories 

 then advocated are instructive, and occasionally 

 amusing. The first reviewed is the spontaneous- 

 coagulation-of-the-blood theory, which he dis- 

 poses of by asserting that the blood is sometimes 

 found fluid, which was a sufiBcient bar to the 

 acceptation of the theory. Strangely enough, 

 however, this appears to be the theory which 

 he attempted to establish in after years, though 

 the objection which he here advanced still held 

 good and was a sufficient refutation of it.* He 



* Fontana is not singular in having advanced a theory 

 that was incompatible with facts which he had previously 

 demonstrated by experiments. Melloni, in his latter 

 days, advocated a theory entirely opposed to results he 

 obtained practically in former years. Miller says, " A 

 consideration of the preceding facts led Melloni to 

 expect that by a combination of screens which allow 

 light of a given colour to pass, radiant heat may be 

 arrested ; and, in fact, he thus effected an apparent 

 separation of light from heat. By transmitting the 

 solar rays, first through a glass vessel filled with water 

 which arrests the less refrangible rays, and then through 

 a plate of a peculiar green glass tinged by means of 

 oxide of copper, which stops the more refrangible rays, 

 a greenish beam was obtained, which was concentrated 



Fontana's 

 criticisms. 



Melloni's 

 theory. 



