468 Journal of Agricultural Research voi. xv. No. s 



rabbits and guinea-pigs are less favorable hosts from the experimenter's 

 point of view. They will not swallow meat unless it is fed forcibly. 

 Even under these conditions the attempted infection is not always suc- 

 cessful in the case of rabbits, and occasionally yields negative results in 

 guinea-pigs. The former were observed to regurgitate meat several 

 minutes after being fed. However, aside from these considerations the 

 size of the intestine and the character of its contents make it rather diffi- 

 cult to isolate the parasites from the intestine of rabbits and guinea-pigs. 

 The intestine of the rat, being considerably smaller, presents the para- 

 sites in greater concentration. In the writer's experience the contents 

 of the intestine of a rat even a few hours after a meal do not seriously 

 interfere with the detection and isolation of the parasites. However, 

 when it is desired to keep the host animals alive for several weeks, rats 

 are not to be relied upon unless they are only lightly infested with the 

 trichinae and are kept in a warm place and protected from drafts. A 

 heavy invasion of trichinae sets up an acute intestinal inflammation in 

 rats and causes their death as early as the third day after artificial 

 infection. A sudden change in temperature or a draft is very likely 

 to bring them down with pneumonia. If it becomes necessary, there- 

 fore, to keep the hosts alive for a month or longer, rabbits or guinea-pigs 

 should be used in preference to rats. Instead of attempting to feed the 

 meat forcibly to these animals, the writer found it more desirable to use 

 the following procedure: The meat is thoroughly chopped up and then 

 digested in an artificial gastric juice for about 18 hours at a temperature 

 of 38° to 40° C. The formula for artificial gastric juice recommended 

 by Ransom (d) has proved entirely satisfactory except that it was found 

 that by reducing the amount of sodium chlorid to 2 grams per 1,000 

 cubic centimeters of fluid, a more thorough digestion of the meat was 

 obtained.^ After digestion of the meat the fluid is slowly decanted and 

 replaced by a 0.7 per cent solution of sodium chlorid. The parasites 

 are allowed to settle to the bottom, and the supernatant fluid is again 

 decanted. This may be repeated until the parasites have been thor- 

 oughly washed. They may then be transferred to a smaller vessel and 

 taken up in a fine pipette with some of the salt solution and forced down 

 the esophagus of rabbits or guinea-pigs. This procedure has invariably 

 resulted in a successful infection. 



Intestinal trichinae were obtained from their hosts as follows : After the 

 animal had been killed by chloroform, the intestine was removed to a 

 large petri dish containing a 0.7 per cent solution of sodium chlorid. 

 The intestine was then slit open from end to end and the mucosa care- 

 fully scraped with the dull edge of a scalpel in order to remove the para- 

 sites from their places of attachment. They were then picked out with 

 the aid of a dissecting microscope by means of a fine pipette, the opening 



> The modified formula is as follows: Water, 1,000 cc.; hydrochloric acid (sp. gr. 1. 19), 10 cc.; scale pepsin 

 (U. S. P.), 2.5 gm.; sodium chlorid, 2 gm. 



