254 SUMMARY OF CURRENT RESEARCHES RELATING TO 



the ratio of the number of Lycopodium spores to the number of cha- 

 racteristic elements of the adulterant, and express the results as the 

 number of characteristic elements counted for every 100 Lycopodium 

 spores. The numbers found for the two sets of counts should not 

 differ by an amount greater than 10 p.c. ; should they do so fresh 

 counts must be made. 2. Mix • 2 grm., or other suitable amount of 

 the sample in which the percentage of adulterant is to be determined, 

 with 0*1 grm., or other convenient amount, of Lycopodium a,ud about 

 20 c.cm. of suspending fluid. Mount a drop on each of two slides, and 

 count ten fields on each. Calculate the ratio of the number of spores 

 of Lycopodium to the number of characteristic elements of j the adul- 

 terant, and express the result in the same form as for the standard 

 mixture. 3. The numbers obtained for the foreign substance in the 

 two sections of work are directly proportional to the amounts present, 

 and a simple calculation gives the quantity sought. 



It will be noted that the novelty of the author's method consists in 

 using the Lycopodium spores as a kind of unitary standard, and 

 thorough admixture is a necessary preliminary to success. There does 

 not seem, however, to be any difficulty in this, and in some cases no 

 further preparation was necessary. But the author found that as a 

 general principle, absolutely necessary sometimes, the spores should be 

 suspended in a suitable liquid, or semi-liquid, and that the choice of 

 this liquid depended on the subject under investigation. He gives 

 full details, and his results attained a very high degree of accuracy. The 

 mixtures relating to his experiments were : wheat-flour and corn-flour ; 

 potato-starch and maize-starch ; dried mustard and dried corn-flour ; 

 wheat-flour and potato-starch ; white pepper and ginger ; white pepper 

 and rice-starch ; gentian-root and cocoanut-shell. 



B. Technique.* 

 (1) Collecting: Objects, including Culture Processes. 



Note on the Isolation of Enteric Organisms.! — F. Denert and 

 G. Mathieu are of opinion that the variable results obtained by different 

 workers on the isolation of enteric organisms by means of malachite- 

 green media is due to variations in the quality of the commercial product. 

 Working with malachite-green (Griibler) they found that Bacillus 

 typhosus multiplied rapidly in solutions of ^^Vo ^^ zw^-^ (with the ex- 

 ception of laboratory strains), that B. paratyphosus A developed better 

 than B. typhosus, and that B. paratyphosus B produced the best growth 

 of all. They recommend the following methods of isolation : — Stools : 

 dilute a portion of the stool with salt solution, and inoculate two tubes 

 containing pepton water added to g^nV o ^^^^ ^^jVo malachite-green re- 



* This subdivision contains (1) Collecting Objects, including Culture Pro- 

 cesses ; (2) Preparing Objects ; (3) Cutting, including Embedding and Microtomes ; 

 (4) Staining and Injecting ; (5) Mounting, including slides, preservative fluids, etc. ; 

 (6) Miscellaneous. 



t Comptes Rendus, clxiv. (1917) pp. 124-5. 



