xl Trans. Acad. Sci. of St. Louis. 



after infiltration with agar-agar, and described the use of this 

 material for imbedding purposes as follows : — 



Tissues can be readily hardened and imbedded for cutting 

 into sections in a hot solution of agar-agar containing formalin. 

 The proportions of the mixture which have so far yielded the 

 best results are nine parts of a five per cent aqueous solution 

 of agar-agar to one part formalin. This mixture can be 

 prepared beforehand and kept indefinitely in an air-tight 

 vessel. The as^ar-aoar should be boiled for several hours, 

 and after the addition of the formalin allowed to clear by 

 sedimentation. The bits of tissue to be imbedded are placed 

 in a wide test-tube or wide-mouth vial containing the mixture 

 previously melted. This is kept at 65-70° C. for an hour or 

 longer, and the tissues are ready to be blocked. After attach- 

 ing to blocks they are placed in strong or absolute alcohol for 

 an hour or two and can then be cut. It is important not to 

 use dilute alcohol. The tissues are stuck to the blocks by 

 means of the agar-agar itself and adhere as soon as the agar 

 becomes cold. No previous hardening of the tissues is at all 

 necessary, fresh tissues can be placed at once into the hot 

 agar-agar-formalin mixture — in fact, fresh tissue is more 

 desirable than that which has been previously hardened, though 

 this can be readily imbedded by this method. But the main 

 advantage of the method, aside from its convenience and sim- 

 plicity, is the fact that the cells of , the tissues are not at all con- 

 tracted or shrunken, and the ordinary methods of hardening 

 have this effect more or less. With sections prepared from 

 fresh tissues by this method the cell-protoplasm fills out the 

 membrane fully, and the granules of the protoplasm, the 

 nuclei, and the cell contours are remarkably distinct. The 

 Avhole process, hardening, imbedding and cutting, does not 

 occupy more than three or four hours, where the tissues are 

 not larger than about one centimeter in diameter. 



Professor A. W. Greeley presented the results of an in- 

 vestigation of the reactions of Paramecia and other protozoa 

 to chemical and electrical stimuli,* 



Two persons were proposed for active membership. 



* Science n. s. 17:980. 



