ZOOLOGY AND BOTANY, MIOBOSCOPY, ETC. 811 



appreciated. Under such circumstances, a combination of the camera 

 and pencil, which the writer has employed since the introduction of 

 the Eastman " bromide paper," may often be found very satisfactory. 

 Selecting the " B " grade, and marking out all undesired parts of the 

 negative, a somewhat under-exposed print is made and developed until 

 the cardinal parts of the picture are visible ; this, when dried, yields a 

 black and white sketch which, after being worked over with Indian ink 

 and hard lead-pencil, presents the appearance of an elaborately finished 

 drawing, and, as such, will be satisfactorily copied by the artist on the 

 block or stone. Where details are very simple, the outlines of the 

 photograph are easily transferred to the drawing-paper by means of the 

 interposed sheet of " graphite " or " carbon " paper and the tracing point. 



But, after all, for the busy worker the direct sketch on paper is 

 frequently the most convenient and economical. It is to be regretted 

 that the di-awing-prisms in use on the Continent are not more generally 

 used among our own microscopists. An experience embracing all the 

 usual forms has resulted in a settling down to the Abbe apparatus as 

 being the most satisfactory, and, due regard to the inclination of the 

 mirror and the warranted size of the sketch being observed, as leaving 

 little to be desired. After a long observation of struggles with the 

 drawing-prisms usually furnished by American and English makers, it 

 is truly refreshing to see with what ease and accuracy complicated 

 contours are followed with this instrument even at the first attempt. 



With any form of drawing attachment the nice balance between the 

 illumination of the microscoj)ical image and that of the paper is an all- 

 important condition ; having had occasion recently to use the Abbe 

 prism to sketch some 1400 sections, the author found a simple device of 

 great service. This consisted of a light stand supporting a small glass 

 plate (10 X 15 cm.), two-thirds of which was "matt," being very finely 

 ground, leaving the remaining third as a clear strip extending in the 

 direction of the greatest length of the plate. The section being well 

 lighted and focused, and the paper adjusted for the drawing, the screen 

 should be interposed between the source of illumination and the 

 mirror, when the object becomes illuminated by a soft diifuse light, 

 very favourable for the rapid and accurate sketching of details. 

 Slight lateral movements of the screen by the left hand soon determine 

 its best position. When a doubt arises as to some detail, a movement of 

 the wrist floods the field with light, enabling an exact observation to be 

 made, while a second change restores the mellow illumination so favour- 

 able for drawing. All this can be done without moving the eye from 

 the tube or taking the pencil from the paper. The position of the screen 

 between the light and mirror is more effective than when the ground 

 glass is mounted as part of the substage apparatus. Those who have 

 never used this simple contrivance in drawing will find it a material aid 

 in many cases. Its fi'equent usefulness on other occasions, as a light- 

 moderator for low-power examinations, will insure it a permanent place 

 on the work-table. 



Instantaneous Photomicrography.* — Herr M. Stenglein, who has 

 been trying to adapt the instantaneous method to photomicrography, 

 recommends a mixture of magnesium, chlorate of potash, and sulphide 

 of antimony, which gives a flash lasting for 1/50-1/30 of a second. The 



* Ceutrall:)!. f. Bakteriol. u. Parasituuk., iii. (1888) pp. 670-4, 702-7 (1 fig.). 



