2540 Journal of Applied Microscopy 



GENERAL LABORATORY TECHNIQUE. 



RAYMOND PEARL, University of Michigan. 



Books and Papers for Review should be Sent to Raymond Pearl, Zoological Laboratory, 

 University of Michigan, Ann Arbor, Mich. 



Model of Cerebral Ventricles. I" ^^e Jour. Anat. and Physiol., Vol. 



XXXVI, Pan -J, 190:^, pp. 1()6-1'2(3, Bar- 

 ratt describes the making of a model of the human cerebral ventricular cavities. 

 A brain was selected which showed but slight evidence of wasting, and in which 

 the cerebral ventricles contained a small amount of fluid. The brain was care- 

 fully removed and placed at once, without being incised or the membranes 

 stripped, in a saturated solution of potassium bichromate, in which it at first 

 floated, slowly sinking at the end of one or two days, but remaining of nearly 

 the same specific gravity as the bichromate solution, for a length of time suffi- 

 cient to allow a well defined hardening of the surface to occur. By this method 

 of hardening a minimum change of form is induced. After hardening was com- 

 pleted, sketches of the outline of the brain and its principal sulci were made. 

 The brain was then sectioned in a vertical transverse plane at intervals of 12}4 

 mm. The slices as they were cut were placed in bichromate solution, and a 

 tracing of each was made without delay. In order to be able to reconstruct the 

 ventricles from the sections it was necessary to have two planes marked out on 

 each section, one horizontal and one sagittal. The former was obtained by 

 placing the brain before sectioning in a frame by the aid of which an incision 

 was made all around its outer surface in a horizontal plane. The second was 

 the mesial plane of the brain, indicated by the great longitudinal fissure and the 

 structures in the middle line at the base of the brain. A plan and front and 

 side elevations of the ventricles were then made and copied onto a block of 

 wood. By this aid and with the sketches a carving of the ventricular cavities 

 was then made. From the figures given it would appear that the procedure 

 followed was very successful. R. p. 



PhotographiDg Living Infusoria. ^^ Biometrika, Vol. I, Part 4, p. 401, 



1902, Simpson describes a method 

 which he has used in obtaining photographs of living ciliates. As apparently 

 such photographs have not been made by other workers, it may be of interest to 

 Journal readers to know the procedure followed. Simpson says : " Ordinary 

 Ilford chromatic plates were used, as also a Leitz 3 lens, which with the associ- 

 ated extension gave a magnification of about 80. The pictures were all taken 

 instantaneously by incandescent light. The proportion of failures was very high, 

 about 70 per cent. The chief difficulty was in obtaining a cell small enough to 

 be wholly included within the magnification of the lens. Ultimately a block of 

 soft paraffin was employed in which a hole was pierced with a fine needle. It 

 was then sectioned with the microtome, and in this way by regulating the thin- 

 ness of the section, a cell was obtained with a minimum of water in which the 

 infusorian could live and yet be in focus all the time. A cover-glass was then 

 superimposed, and as it was held in position by a generous application of vas- 

 eline round the edge, I was able to take photographs in a horizontal position. 

 Some of the photographs were sadly lacking in definition, but it is a matter of 

 extreme difficulty to calculate and adapt that amount of water in the cell which 

 is sufficient for the free movement and life of the protozoan and yet is not too 

 great to allow it to get out of focus during the exposure." r. p. 



