592 SUMMARY OF CURRENT RESEARCHES RELATING TO 



out that fat is an important reserve-substance of bacteria, being de- 

 posited in the form of drops in the cytoplasm of these plants. He 

 had also found that these fat-drops are an important criterion for 

 many species, but that at certain stages the appearances of spores 

 and ' fat-drops so closely resembled each other that they could not 

 be distinguished by the ordinary known reactions. He now finds 

 that a solution of 5 grin, chloral hydrate in 2 grm. water is an excellent 

 medium for distinguishing between fat-drops and spores. If, for ex- 

 ample, a sporange of Bacillus tumescens which contains both a spore and 

 fat-drops, be placed in this reagent, the fat is at once dissolved, while the 

 spore stands out quite distinctly. This procedure renders unnecessary 

 any special method for staining spores ; for if the material be treated 

 by the choral solution, it brings out the spore too distinctly to be mis- 

 taken for anything else. 



Eau de Javelle also has a characteristic reaction to ripe spores and 

 fat-drops. If some bacterial material containing both spores and fat- 

 drops be stirred up with a drop of Javelle's solution, it will be found that 

 the protoplast of the sporanges and of the bacterial oidia is dissolved, 

 while the membrane is at first unaffected. Like the membrane of the 

 spore, bacterial fat is also resistant to the action of eau de Javelle, and 

 by means of this reagent can be macrochemically isolated. Bacterial fat 

 then is easily soluble in chloral hydrate, and is only slowly attacked by 

 eau de Javelle. 



(3) ^Cutting, including' Imbedding and Microtomes. 



Delepine Improved Microtome.*— Messrs. E. and J. Beck have made 

 some additions and improvement to the Delepine microtome previously 

 described (fig. 121). The knife-carrier and rails are longer, the stand 

 is of larger size, and has an extra supporting upright. The knife-carrier 

 is 9 in. long, and is provided with two handles, forming a tie at each 

 end. The whole is made from one solid gun-metal casting. The carrier 

 has a travel of 7J in. without leaving the rails. Along the upper faces 

 of the carrier are two grooves in which run the clamps holding the 

 razor. These may be placed so that the razor is either at right angles 

 or at any obliquity to the angle of cut, the razor being held rigidly at 

 each end. The clamps are so arranged that they are higher than the 

 knife-edge, and thus the entire length of a 6-in. blado may be used for 

 an oblique cut. The blade itself may be tilted by the set-screws of the 

 clamp. The illustration shows the instrument arranged for the oblique 

 knife. 



Fiori's Automatic Microtome.f — Prof. A. Fiori has devised an auto- 

 matic microtome (fig. 122) in which, by a double and simultaneous 

 movement of the knife-bearer and object-carrier, the knife and prepara- 

 tion are made to meet in a very neat way. The movement is a gliding 

 one, and is therefore similar to that of the sliding microtomes, though 

 obtained in a different way and by means of a lighter instrument. The 

 principal features in this instrument are that the knife-carrier has 

 fixed to its lower end a grooved plate with a handle at one end. In the 



* R. and J. Beck's List, 1901. Cf. this Journal, 1900, p. 128. 

 t Malpighia, xiv. (1900) pp. 411-24 (6 figs.). 



