EFFECT OF TEMPERATURE ON THE BLADDER- WORMS. 533 



The most thorough investigations regarding the power of resistance 

 of the bladder-worms of the pig are due to Perroncito. Although at 

 first inclined to the opinion that it required a temperature of at least 

 125 C. (257 F.) to render the bladder-worms harmless, 1 he was after- 

 wards enabled, by means of a more exact method of investigation, to 

 establish that the latter are certainly killed when the temperature of 

 the surrounding fluid reaches 50 C., or even below that, and when the 

 worms remain in it longer than a minute. 2 What impelled Perron- 

 cito to these renewed researches was the opposition to his first results 

 on the part of Pellizzari, who, like Lewis and Cobbold, had fixed the 

 fatal temperature at about 60 C. 



The difference between these results is explained in this way, that' 

 the experiments on which they are founded were made sometimes on 

 large masses of flesh, sometimes on the isolated bladder-worms, where 

 the surrounding temperature would of course affect the actual objects 

 with varying rapidity and completeness. 



To fix the absolute power of resistance possessed by the bladder- 

 worms, it is best to take the isolated worms, as Perroncito did in his 

 later experiments. He placed them on Schultze's warm stage, and 

 observed the effects of increasing warmth. While the bladder-worms 

 at low temperatures (under 16 to 20 C.) usually remain motionless, 

 after passing above 30 to 35 C., more or less lively contractions of the 

 body as a whole, and particularly of the suckers and proboscis, are 

 observed. The movements become still more energetic at a tempera- 

 ture of 42 to 45 C., but then suddenly stop, in some cases at 45 C. 

 or 46 C., or only at 48 C., and do not begin again even if the 

 worm be gradually cooled down to the temperature of the air, and 

 allowed to rise again. Only in one case did a Cysticercus survive a 

 temperature of 49 C. ; but it became motionless at 50 C. 



Perroncito showed distinctly that the motionless state is in reality 

 death, not only by the use of the warm stage, 3 but by proving experi- 

 mentally " that such overheated bladder-worms had lost their power 

 of development." One of his students, a young Dr. M., swallowed on 

 two different occasions (January and March) a bladder-worm which 

 had been thus heated up to 50 C., and remained free from tape- 

 worm. 4 



In order to ensure the death of the bladder- worm in cooking, a 



1 "Delia panicatura degli animali," Ann. R. Accad. Agricdt. Torino, t. xv., 1872. 



2 " Sulla tenacita di vita del Cysticerco della cellulosa," ibid., t. xxx., 1876 (abridged 

 in Moleschott's Unters. zur Naturlehre, Bd. ix., No. 37), and "Delia grandine e panicu- 

 latura nelT uomo e negli animali," ibid., t. xix. 



3 The attempt to prove death by the "inhibition method" yielded but doubtful 

 results, so that we may omit it. 



4 " Sulla tenacita, &c.," p. 21. 



