and Laboratory Methods. ^^^^ 



CYTOLOGY, EMBRYOLOGY, 



AND 



MICROSCOPICAL METHODS. 



Agnes M. Claypole. 



Separates of papers and books on animal biology should be sent for review to 



Agnes M. Claypole, Sage College, 



Ithaca, N. Y. 



CURRENT LITERATURE. 



Sjobring, N. Ueber das Formol als Fixinings- -p^e author says that the opinions of 



fliissigkeit. Allgemeines ueber den Bau ^ 



der lebenden Zellen. Anat. Anz. 17: 273- formol as a fixing fluid are not, in gen- 



304, 3 Abb, 1900. Abstract in Zeis. f. wiss. gj-^i favorable. Many writers say it is 



Mikr. u. f. Mikr. Techn. 17: 337-340, 1900. 



decidedly unfitted for the finer preserva- 

 tion of cell tissue. According to the writer formol does not merit this condemna- 

 tion, caused by the fact that these writers have failed to discover the small point 

 upon which the successful use of formol depends. A distinction is made 

 between the " Formol " of the firm, Meister, Lucius, u. Briining, Hochst a 

 Main, and the " Formalin " of Actien (Sobering) of Berlin. Formalin is not 

 so suitable for histological work as formol. It must be understood that formol 

 is only a fixing agent, not a hardener. Material fixed in formol should be 

 hardened in 95 per cent, alcohol for 48 hours or longer, at least mammalian 

 tissue should be so treated. For tissue containing much water, different 

 strengths of alcohol are desirable. For Anodonta, 50 per cent, alcohol is most 

 favorable. It is probably this point that causes the various results obtained by 

 authors in the use of formol. The action of formol on tissue is probably an 

 oxidation similar to that of osmic acid. The first requisite for a successful fixing 

 fluid is that it should be approximately isotonic with the protoplasm. Formol, 

 in comparison with the tissues of mammals, should have the isotonism of 8 to 10 

 per cent, formaldehyde (1 pt. formol to 4 of water), but not all tissues have the 

 same tension. For mammals, the following process gives the best results : Fixa- 

 tion in formol, 1 :4 water for 48 hours or longer; direct into 95 per cent, alcohol 

 for at least two days. In this way the resting nuclei, red blood cells, intracellular 

 cement between epithelial cells, fibrin, fibrinoid degeneration of connective 

 tissue, gelatinous and other albuminous exudates, are especially well 

 preserved. The metakinetic stages of mitosis are not successfully obtained. 

 Formol is not especially good for nerve-tissue — preservation is good, but the 

 staining capacity is lessened — stronger and warmed stains are necessary. 

 Some methods of staining are especially applicable after formol fixation. Heiden- 

 hain's iron-alum-haematoxylin is especially good when used in a modified way. 

 Strong solutions were found most effective. Ha^matoxylin of a concentrated 

 aqueous solution and iron-alum for the mordant, in a 5 per cent, solution, allowed 

 to act for three hours. For differentiation, the same strength or a one-half dilu- 

 tion was used. The stain was allowed to act for one hour, with some warming. 

 Anilin blue was used for a preparatory stain ; concentrated alcoholic solution in 

 50 per cent, alcohol was diluted one-half with water. Crystal-violet in a 1 per 



