G. NATURAL HISTORY AND ZOOLOGY. 2*79 



to Professor Abbe, by no microscope can parts be distinguish- 

 ed if they are so near to each other that the first bundle of 

 light rays, produced by diffraction, can no longer enter the 

 objective simultaneously with the undinraeted cone of light. 

 12 A, IX., 191. 



THE SAND-BLAST FOR MAKING MICROSCOPIC SLIDES. 



The proceedings of the Queckett Microscopical Club men- 

 tion that the sand-blast has been successfully employed by 

 H. F. Hailes for excavating hollows in glass slides, to be used 

 as cells for microscopical uses. For wet mounting, it is said, 

 the roughness of the bottom is no hinderance to mounting 

 objects in balsam, as the lower surface of the cell is rendered 

 perfectly transparent by contact with the mounting material. 

 For dry mounting it is also said to answer well. 



DETERMINATION OF BLOOD STAINS. 



According to the report of a recent commission, we learn 

 that by the use of the microscope, either alone or associated 

 with chemical analysis and the spectroscope, it is now possi- 

 ble to obtain certainty as to the question whether stains are 

 really those of blood or not, although it is hardly practicable, 

 except when the stains are recent, to decide whether they 

 are from man or belong: to some other animal. 



If the stains are old and the blood is changed, a reaction 

 with the tincture of guaiacum will suggest the presence of 

 blood ; but its actual existence can not be ascertained with- 

 out spectrum examination, or the production of crystals of 

 hydrochlorate of hematine. One of the two is sufficient. 

 1 A, December 5, 1873, 291. 



LIFE IN DEATH. 



At the meeting: of the Swiss Scientific Association, in An- 

 gust, 1873, Professor Karsten stated that the development 

 and increase of embryonic cells contained in the cell fluid con- 

 tinues for a lono;er or shorter time after the death of the or- 

 ganism, unless suppressed by great dryness, extremes of tem- 

 perature, want of oxygen, or chronic agents that interfere 

 with assimilation. He considered the bacteria, vibriones, etc., 

 present in closed cells of the tissues of diseased or dead or- 

 gans, and regarded as the carriers of contagion, to be in real- 



