16 DR. E. KLEIN. 



such as ordinary French gelatine, best Swiss gelatine, much 

 recommended to photographers by Dr. Eder of Vienna, best 

 French gelatine, called gold-label gelatine, isinglass, a peculiar 

 lichen-gelatine used by Chinese cooks to get a very firm jelly, and 

 various other kinds of gelatines ; and after a great many experi- 

 ments, both time-consuming and patience-trying, to enumerate 

 which would be a very unnecessary infliction on the reader, I 

 have found best answering our purpose a gelatine solution 

 prepared in the following manner : one part of " gold-label 

 gelatine " (the tablets in which it is sold being cut up into 

 small strips) is soaked overnight in six parts of cold water, it 

 is then dissolved on the water bath ; this solution has a slightly 

 acid reaction; to it is added carbonate of sodium just sufficient 

 to give it a neutral reaction. While quite hot it is filtered 

 through filter paper once or twice. (It must be borne in mind 

 that the filter paper, the vessels receiving the solid gelatine or 

 the filtrate, and all other vessels subsequently used for its re- 

 ception, are perfectly disinfected by overheating them.) The 

 process of filtering is carried out by using hot filters and filter 

 paper, keeping up the warmth by placing at two opposite sides, 

 as close to the filter as practicable, Bunsen burners. The fil- 

 trate is tolerably clear, but can be obtained perfectly clear by 

 adding to it after neutralisation egg albumen, and then boiling 

 it for several minutes. In this latter case it may be filtered 

 through calico or flannel previously disinfected. To the fil- 

 tered gelatine are then added three parts (not three times its 

 volume) of the above pork broth, so that we have now alto- 

 gether one part of solid gelatine, six parts of water, and three 

 parts of pork broth, which would be equal to one part of solid 

 gelatine in nine parts of fluid, or ll^V per centum. This mix- 

 ture is received in several sterilised flasks, closed well with 

 long and thoroughly sterilised cotton-wool plugs, and is sub- 

 jected to boiling for 5 — 10 minutes. While still boiling, and 

 just before removing from the flame, the mouth of the flask is 

 covered with a cotton-wool cap, and a beaker is inverted over 

 it. The flasks are then placed in the incubator and kept there 

 at 32 — 35° C. for twenty-four hours, after which they are again 



