The Microscope. 375 



Brachionus is to rapidly kill tlie eggs by immersing in chrom-acetic 

 acid; this gives rise to little or no distortion. The eggs are then 

 placed in weak alcohol, and later transferred to strong. The wi'iter 

 states that picro-snlphuric acid produces great distortion, and cor- 

 rosive sublimate does not penetrate. Htematoxylin is the stain to be 

 used; carmine is useless. Clarify in creosote. Paraffin penetrates 

 with difficulty. 



Heidenhain's Staining Method. — Prof. R. Heidenhain finds 

 that the following slight modification of his well-known staining 

 method yields the most beautiful results. Tissues hardened in alco- 

 hol, or better in a saturated solution of picric acid fii'st, and then in 

 alcohol, are left for twelve to twenty-four hours in an aqueous 

 solution of hsematoxylin (| per cent.), and then placed for twelve to 

 twenty-four hours in i per cent, solution of "simple yellotv chromate 

 of potassium (instead of the red double chromate). The usual 

 dehydration with alcohol, penetration with xylol, and imbedding in 

 paraffin, follow. — Jr. R. M. Sac. 



ABSTRACTS, 



THE THERMAL DEATH-POINT OF PATHOGENIC 

 ORGANISMS. 



Dr. Geo. M. Sternberg has completed the series of experiments 

 to which we referred in an editorial in the July number of The 

 Microscope, and has published his observations in the American 

 Journal of the Medical Sciences for July, 1887. 



All of the experiments recorded relate to moist-heat, — that 

 is to say, the test- organisms have, in every case, been in a moist 

 condition, in fluid cultures. The effect of dry heat upon desiccated 

 organisms is quite another question. 



This has been studied by Koch and Wolff hugel, who have sum- 

 marized the results of their experimental work as follows : 



(1). A temperature of 100^ C. (212^ F.) maintained for one 

 hour and a half, will destroy bacteria which do not contain spores. 



(2). Spores of mould-fungi require for their destruction in hot 

 air a temperature of from 110^—115° C. (230—239° F.) maintained 

 for one hour and a half. 



(3). Bacillus spores require for their destruction in hot air a 

 temperature of 140*^ C. (284*^ F.) maintained for three hours. 



