604 SUMMARY OF CURRENT RESEARCHES RELATING TO 



tion ; so that when excessive the reversal of the characters of negative 

 double refraction is obtained. 



Degenerated fibres in a nerve-trunk can be detected by this method, 

 which is quite simple and satisfactory. 



Cooling Paraffin Section Blocks.* — The useful de\ice of smearing 

 the surface of the paraffin block to prevent the curling of sections is, 

 says E. von Lendeufeld, attended with two inconveniences ; one is that 

 you must wait while the paraffin sets, the other that the block softens 

 from the repeated application of hot paraffin. 



These inconveniences may be obviated by directing a current of cool 

 air on the block. A rubber tube is connected at one end with a water- 

 bellows, the other with a glass tube drawn out to a point. The tube is 

 provided with a stop-cock to regulate the pressure of air. The air 

 passes through a Woulff's bottle to the tube ; in the bottle are placed 

 pieces of ice to cool the air. 



Methods in Plant Histology.f — Prof. C. J. Chamberlain's work on 

 histological technique for botanical students will be very acceptable to 

 many workers. The first part deals with the principles and processes 

 of microtechnique, while the second part is devoted to the application of 

 the principles to special cases. In the first part are considered the 

 apparatus ; the reagents for killing, fixing, and staining ; the procedures 

 necessary in the paraffin, celloidin, and glycerin methods. In the second 

 part a series of forms has been selected for demonstration, which will 

 serve not merely for practice in microscopical technique, but will also 

 furnish the student with preparations for a fairly satisfactory study of 

 plant structures from the Algae up to the Angiosperms. 



Chabry's Apparatus.! — Fr. Kopsch describes an improved Chabry's 

 apparatus for observing ova and minute objects. The alterations chiefly 

 consist in mechanical improvements, the apparatus being practically 

 the same as that previously described in this Journal. 



Methods of Determining the Abundance of Bacillus coli communis 

 in River Water.§ — Prof. E. 0. Jordan adopted two methods : one, the 

 carbol-broth method for highly polluted waters ; the other the dextrose- 

 broth method for relatively pure waters. In the first procedure a 

 measured quantity of water in carbol-broth was submitted to a pre- 

 liminary incubation. The broth was prepared by adding 1 ccm. of 1 p.c. 

 solution of carbolic acid in sterile water to tubes containing 9 ccm. of 

 sterile broth. The broth was first rendered neutral to pheuolphthalein, 

 and then acidified by the addition of 5*5 ccm. of normal acid per litre. 



1 ccm. of a suitable dilution of the water was added to a tube and in- 

 cubated at 38° C. for 18-24 hours. Plates were then made of litmus- 

 lactose-agar (5 ccm. normal alkali per litre). If red colonies developed 

 on the medium at 38° C, they were transferred to tubes and tested for 

 gas formation, indol-production, coagulation of milk, and liquefaction of 

 gelatin. 



In the alternative procedure, the water was introduced directly into 



* Zeitschr. wiss. Mikr., xviii. (1901) pp. 18-9. 

 t Univ. Chicago Press, 1901, vi. and 159 pp. and 74 figs. 



t Internat. Monatschr. Auat. u. Pkys., xvii. (1900) pp. 125-37 (2 figs.). Cf. this 

 Journal, 1888, p. 801. § Journ. Hygiene, i. (1901) pp. 295-320. 



