2Q8 HOW TO WORK 



twenty drops of a strong saturated solution of bichromate of potash 

 to an ounce of the strong glycerine. By this plan, the hardening 

 effects of these reagents upon the finest nerve tissues are improved, 

 while the granular appearance which is caused by aqueous solutions 

 of these substances is much less. Sometimes advantage seems to 

 result from mixing a little of the chromic acid with the acetic 

 acid solution of glycerine. 



If desired, sugar may be substituted for glycerine in all the fluids 

 employed, including the carmine and injecting fluids ; but glycerine, 

 although more expensive, possesses many advantages, and, as far as 

 I am able to judge, is the best viscid medium to employ for general 

 purposes. 



One great inconvenience of syrup arises from the growth of fungi, 

 especially in warm weather. Camphor, creosote, carbolic acid, 

 naphtha, prevent this to some extent ; but it^is a disadvantage from 

 which strong glycerine is perfectly free. Sometimes, too, crystallisa- 

 tion occurs, and destroys the specimen. In using first a syrupy fluid, 

 and then glycerine, to the same specimen, it must be remembered 

 that the two fluids mix but slowly, so that plenty of time must be 

 allowed for the thorough penetration of the medium used last. 



I keep various tests, such as alcohol, ether, the various acids and 

 alkalies, and other tests in the form of viscid solutions made with 

 glycerine or sugar. The reaction of the iodine tests for amyloid 

 matter, starch and cellulose, is much more distinct when employed 

 in this way. The plan is, to allow the texture to be tested to be 

 thoroughly saturated with the strong glycerine solutions, and then to 

 add water. In the course of a few hours the reaction takes place 

 very strongly. 



375. Of the Injection of Solutions of various Chemical Com- 

 pounds dissolved in Glycerine. AVhen it is desired to subject the 

 tissues of an organ or of the body generally to the influence of 

 certain chemical solutions, these may be injected and oftentimes the 

 most perfect results are obtained by this process. However care- 

 fully small pieces of tissues may be soaked in fluids the action is 

 irregular, and while the process has gone too far upon the surface, 

 the interior often escapes entirely. But by injection, every part of 

 the tissue is acted upon and almost precisely in the same degree. 

 Many beautiful results are to be obtained by carrying out this plan, 

 and the skilled observer will be able to suggest to himself many 

 experiments likely to lead to most valuable conclusions, particularly 

 in connection with the subject of development. The calcareous 

 matter of bone and other tissues may be dissolved out in this way 

 by very slow degrees without disturbing in the least the arrangement 



