ZOOLOGY AND BOTANY^ MIOKOSCOPY, ETC. 1049 



thickness of the section is a matter to be wholly determined by tlie 

 particular character of the tissue or object to be examined and studied. 

 Of course, no one having any correct knowledge of tissue structure 

 would think of attempting to cut a section of bone, or of the skin of the 

 heel, to the same measure of thinness that would be necessary to demon- 

 strate bacilli in a section of tuberculous lung." 



" If coarse details only are required, then a thick section properly 

 cleared, and a low-power objective, will answer the purpose in view ; but 

 when the finest possible details of a histological or pathological specimen 

 are sought by the aid of a high-power objective, a section just thin enough 

 to hold the tissue elements together will not be too thin — the thinner the 

 better — provided the section has been handled from beginning to end in 

 the highest style of the beautiful art. In other words, a very thin, 

 evenly-cut section — the 1/3000 in. — is of no more use or value than a 

 section the 1/50 in. thick, if it — the thinner section — has not been 

 perfectly cleared up and well mounted." 



In reply * to Dr. Eeeves's criticism, the editors " still insist that our 

 sections must have a thickness that will include as many layers as can 

 be clearly studied; for the details of a specimen cannot be observed 

 unless it is thick enough to show the arrangement of its parts. As for 

 studying the finest possible details, such as the structure of or changes 

 in individual cells, no section, however thin, will serve the purpose. 

 Other methods must then be employed." 



Baltzae, G., and E. Zimmeemann. — Mikrotom mit festem Messer und selbst- 

 thatigen Vorschub des Objekts. (Microtome with fixed knife and automatic 

 movement of the object.) 



German Patent, 12th March, 1888, No. 45,504. 

 Campbell, D. H. — ParaflSn-Einbettungmethode fiir pflanzlicbe Objecte. (Paraf- 

 fin imbedding methods for vegetable objects.) 



Naturwiss. Wochenschr., II. (1888) p. 61. 



C4) Staining and Injecting'. 



Methyl-green for observing the Chemical Reaction and Death 

 of Cells.f — Prof. A. Mosso used for his researches on the reaction between 

 methyl-green and blood- or pus-corpuscles, a watery 1 per cent, solution 

 of sodium chloride in which • 2 per cent of methyl-green was dissolved. 

 To observe the action of this solution on the red corpuscles it is only 

 necessary to prick the finger, and touch a drop of the solution placed on a 

 slide with the blood. This preliminary examination, made with an 

 apochromatic 20 mm., aperture 1 • 30, oculars 4 and 12, was supple- 

 mented by observations in the moist chamber at periods of 6 and 24 

 hours. The result of these experiments showed that if cells were 

 quite healthy or in their proper working condition they did not become 

 stained, but if this condition became weakened they stained violet, 

 then bluish-green, and finally green. Dead cells became coloured 

 green at once. 



The solution was also noted to have a toxic action indicated by 

 the death of the cells, and their consequent staining, as their enfeeblement 

 began and death took place. The cells used for the examination 

 were red and white corpuscles of the blood of fishes, frogs, &c., cilia 



* The Microscope, viii. (1888) p. 248. 

 t Arch. Ital. Biol., x. (1888) pp. 29-39. 



