156 SUMMARY OF CURRENT RESEARCHES RELATING TO 



This metliod has enabled the author to trace out the history of 

 the endoderm, and the precise origin of the nerve-cords, nephridia, 

 salivary glands, larval glands, &c. 



Preparing Mammalian Ovaries for Examination of Graafian 



Follicles.* — Dr. W. Flemming recommends a 2 per cent, solution of 

 osmic acid, and also a mixture of chromic, osmic, and acetic acids 

 for hardening ovaries and safranin or gentian- violet for staining the 

 sections. 



Preparation of Connective Tissues.f — Herr T. Ognew condemns 

 most of the ordinary fixative agents, on account of their rendering 

 connective tissue cells and their processes imperceptible. His best 

 results were obtained from 1 per cent, solution of osmic acid. In 

 using this, however, several precautions must be observed. The 

 length of the embryo must be from 2-8 cm. The embryo must 

 be still warm when placed in the hardening fluid. It must not remain 

 in the acid longer than twenty-four hours. Preparations of connective 

 tissue cannot be said to be properly stained unless the cells and their 

 finest processes stand out quite clearly. 



For the osmic acid preparations the best stain is a mixture of a 

 saturated watery solution of safranin and Bohm's hsematoxylin. 

 Five to twenty drops of the hasmatoxylin solution are added to a 

 medium-sized watchglassful of the safranin solution. After mixing 

 it is necessary to remove the precipitate which arises, by filtration. 

 Preparations stained by this method can be mounted in glycerin 

 without detriment to their colour. 



Preparing Spinal Cord. — At the December meeting of the Society 

 a section of the spinal cord of the ox, prepared by Mr. C. Eobertson, 

 Demonstrator of Anatomy at Oxford, was exhibited by Dr. Beale, and 

 the method of preparation is thus described by Mr. Eobertson. 



" Portions of the warm cord about an inch long are placed in weak 

 spirit (10 over proof) from four or five hours, then transferred to 

 a 6 per cent, solution of bichromate of potash for six days, care being 

 taken during the process of hardening to remove with a razor thin 

 sections from the ends to allow the solution to thoroughly penetrate 

 to the interior of each piece. The process of hardening is completed 

 by transferring to weak spirit for two days, then to strong for two or 

 three more days, when the cord can be kept till wanted for sections. 

 Portions of the cord are stained before sections are made by soaking 

 for twelve hours in a solution of good picrocarmine, washed in weak 

 spirit, and soaked for a short time in absolute alcohol, which should 

 be used to wet the razor in cutting. The sections are cleared in oil 

 of cloves, and mounted in dammar varnish or Canada balsam dissolved 

 in benzole in the usual way. 



I have tried most of the methods recommended in the text-books 

 for demonstrating the structure of the spinal cord, brain, ganglia, 

 &c., and find that none of the methods recommended bring out the 



* Arch. f. Anat. u. Physiol. (Anat. Ablheil), 1885, pp. 221-44 (2 pis.), 

 t Ibid., pp. 437-49 (1 pL). 



