40 THE AMEKICAN MONTHLY [March, 



All this may be obviated, and an inexperienced manipulator produce as 

 good a carmine fluid as one who is thoroughly conversant with micro-injec- 

 tions by determining, before making the fluid, the exact amount of acid 

 which it will take to neutralize a given quantity of ammonia ; that quantity 

 which is to be used in the fluid made. To this end, take a dram of the aqua 

 ammonial, which is to be used, and add to it, gradually, with constant stir- 

 ring, acetic acid, testing with blue litmus paper. The instant the paper 

 changes to red stop adding the acid, and note the amount which has been 

 used. Suppose that it is i| "drams, as was the case the last time I made up 

 an injection fluid, then the proportion of acetic acid to ammonia will be ii 

 to 6, and if the entire amount of ammonia to be used be 4 drams, as in the 

 formula to be given, then the amount of acid needed will be 71 drams. In 

 this way the proper amount of acetic acid to ammonia mav be found in any 

 formula. Having had uniformly most excellent results with the following, I 

 can unhesitatingly recommend it as one of the best, if not the best, of the 

 gelatin carmine warm flowing masses : 



CARMINE SOLUTION. 



Carmine No. 40, 4 drams. 



Aqua Ammonial Fort, 4 drams. 



Water, 6 ounces. 



Grind the carmine in a mortar, gradually adding the water, then add the 

 ammonia, and heat gently until the carmine is dissolved. 



GELATIN SOLUTION. 



Gelatin, i^ ounces. 



Water, y-^ ounces. 



Soak the gelatin in the water until soft, and then dissolve by heating. 



Take Ave ounces of the gelatin solution and add to it the solution of car- 

 mine. Add to the remainder of the gelatin solution sufficient acetic acid, 

 as found by pi'evious trial, to neutralize the 4 drams of ammonia contained 

 in the carmine solution. Heat the solution containing the carmine and that 

 containing the acid to about the same degree, by placing the bottles contain- 

 ing them in a pan of water kept hot on a stove or over a lamp. Add grad- 

 ually, with constant stirring, the gelatin solution containing the acid to that 

 containing the carmine. Filter while hot through two thicknesses of flannel. 



The fluid can be poured into the flannel shaped into a bag, when pressure 

 on the sides of the bag will cause the contained fluid to pass through the 

 cloth. Add 4 drams of chloral hydrate, and shake until dissolved. 



The chloral will preserve the mass for quite a long time, but, if it is to be 

 used within a day or two, the chloral is not necessary. A mass, made up 

 by the formula given, is sufficient in amount to inject a small cat or rabbit 

 entire. Should a mass be needed only for a single organ, the quantity of all 

 the ingredients can be reduced, retaining the relative proportions. 



In my experience injection of the whole animal gives the best results, ex- 

 cept when special injections of a single organ is to be made with two fluids, 

 when careful injections of the organ itself is better. In all cases a manometer 

 should be used, together with some form of constant pressure apparatus. A 

 syringe cannot be recommended, but the injecting jar of Prof. Gage is very 

 useful, and less complicated than a water pressure apparatus. One can 

 easily be extemporized out of a wide mouth bottle, and fitted with a manom- 

 eter made from a piece of bent glass-tubing fastened to an upright board, 

 with a scale in inches or millimeters marked on it. The only other articles 

 necessary are a tin box, with a shelf inside, on which to lay the animal while 

 injecting ; a sheet of glass large enough to cover the box, a thermometer, a 



