ARTIFICIAL CIRCULATION. 267" 



lymph, and the excised liver to secrete bile, for hours after the 

 rest of the animal has been consigned to the dust-bin. 



Circulation of Warm and Cold Blood. — For this purpose, 

 blood may be used either at the temperature of the room or of 

 the body ; but these have not exactly the same effect, and experi- 

 ments made with blood at one temperature must not be com- 

 pared indiscriminately with those made with blood at another. 

 Professor Ludvvig, to whom we owe this method, has discovered 

 by its means the curious fact that tlie muscles of a warm- 

 blooded animal may be artificially endowed with the pro- 

 perties of those of a cold-blooded one. Those of a frog or other 

 cold-blooded animal retain their irritability, and contract, 

 when stimulated, for a long time after they have been removed 

 from the body ; while those of warm-blooded animals quickly 

 lose theirs, and will no longer contract on the application of a 

 stimulus, no matter how powerful it may be. But if the 

 muscle of the warm-blooded animal be quickly cooled by pass- 

 ing a stream of cold blood through its vessels immediately after 

 it has been excised from the body, and before it is stimulated, 

 it will retain its irritability for a long time, and respond to 

 stimuli again and again, like that of the cold-blooded frog. 



Fever. — In the same way, by supplying the heart of a mammal 

 with cold blood, it may be made to resemble that of a frog or 

 turtle ; while, on the other hand, if the heart of a frog be 

 supplied with warm blood, it will become like that of a mammal ; 

 and if the temperature be still further raised the quick and 

 weak beats of fever are produced. 



Mode of Conducting Artificial Circidation. — When we wish to 

 pass blood, at the ordinary temperature of the room in which 

 we are working, through any organ, we defibrinate the blood of 

 the animal itself from which the organ has been obtained, or 

 the blood of an animal of the same species ; dilute it some- 

 what with salt solution of 1 per cent. ; and put it into a flask 

 with two necks, one of which is near the bottom of the flask, 

 as seen at A, Fig. 131. We then introduce a cannula into the 

 principal artery of the organ, and ligature, if necessary, the 

 smaller arteries and branches ; fill it carefully with blood by 

 means of a fine pipette, so that no air-bubble remains in it, and 



