1480 
nutrition and the period of incubation is produced by raising the 
protein- and the fat-content of the diet that evolves polyneuritis. 
3. On the ground of the first conclusion the hypothesis of a 
neuritie poison in the diet, or a toxin, originating from the food in 
the intestinal canal, as probable causative factors of feeding-poly- 
neuritis, must be abandoned, while probably no endogenous neuritic 
poison is in operation. 
4. According as the food is composed it plays the principal part 
in preventing, but an inferior part in producing the disease. 
5. Feeding, most likely causes an increased consumption of anti- 
neuritic substances. It seems hardly permissible to eonelude with 
Brappon and Cooprr and with Funk that carbohydrates promote the 
katabolism much more than, for instance, proteins do. 
6. The digestion of polished rice in fowls is aided through the 
admixture of cellulose to the food, not however, through the addition 
of the antineuritie extract from ricepolishings. The admixture of 
cellulose may exert a favourable influence upon the condition of 
nutrition; it would seem, on the other hand, that the outbreak of 
the disease is accelerated by it rather than retarded. 
7. The conclusions regarding the causative or the prophylactic 
agency of certain factors in polyneuritis gallinarum, are, in so far 
as they are based upon a shortening or a lengthening of the period 
- of incubation, more or less doubtful on account of the considerable 
individual differences, exhibited by the animals experimented upon, 
even with a uniform treatment. 
Utrecht, January 1916. The Institute of Hygiene of the 
Utrecht University. 
Physics. -— On the Brownian Movement in Gases’. By Miss A. 
SNETHLAGE. (Communicated by Prof. J. D. vaN DER WAALS). 
(Communicated in the meeting of February 26, 1916), 
Among the different derivations of the deviation which a particle 
suspended in a gas or liquid obtains in a time ¢, there is one of 
VON SMOLUCHOWSKI ®), in which only kinetic considerations are made 
use of. According to von Smo.ucHowski this derivation will only 
hold for gases, and that only when the dimensions of the particle 
are small with respect to the mean free path of the surrounding 
molecules. As the writer himself observes, there is still something 
1) Von Smorvenowskr. Ann. der Phys. 21 p. 769 (1906), 
