130 PHILOSOPHICAL TRANSACTIONS. [anNO 1666. 



Secondly, That you constantly observe the pulse beyond the quill in the dog's 

 jugular vein (which it acquires from the impulse of the arterial blood :) For if 

 that fails, then it is a sign the quill is stopped by some congealed blood, so that 

 you must dravi' out the arterial quill from the other, and with a probe open the 

 passage again in both of them, that the blood may have its free course again. 

 For it must be expected when the dog that bleeds into the other has lost much 

 blood, that his heart will beat very faintly, and then the impulse of blood being 

 weaker, it will be apt to congeal the sooner, so that at the latter end of the work 

 you must draw out the quill oftener and clear the passage; if the dog be faint 

 hearted as many are, though some stout fierce dogs will bleed freely and uninter- 

 ruptedly till they are convulsed and die. But to prevent this trouble, and make 

 the experiment certain, you must bleed a great dog into a little one, or a mastiff 

 into a cur, as I once tried, and the little dog bled out at least double the quantity 

 of his own blood, and left the mastiff dead upon the table ; and after he was un- 

 tied he ran away and shaked himself, as if he had been only thrown into water. 

 Or else you may get three or four several dogs prepared in the same manner; 

 and when one begins to fail and leave off bleeding administer another, and I 

 am confident one dog will receive all their blood, (and perhaps more) as long 

 as it runs freely, till they are left almost dead by turns : provided that you let 

 out the blood proportionably as you let it go into the dog that is to live. 



Thirdly, I suppose the dog that is to bleed out into dishes will endure it the 

 better if the dogs that are to be administered to supply his blood be of near an 

 equal age, and fed alike the day before, that both their bloods may be of a near 

 strength and temper. 



There are many things I have observed upon bleeding dogs to death, which 

 I have seen since your departure from Oxford, whereof I shall give you a re- 

 lation hereafter ; in the mean time, since you were pleased to mention it to the 

 Royal Society, with a promise to give them an account of this experiment, I 

 could not but take the first opportunity to clear you from that obligation, &c. 



So far this letter : the directions whereof having been carefully observed 

 by those who were employed to make the experiment, have hitherto been at- 

 tended with good success ; and that not only upon animals of the same species 

 (as two dogs first, and then two sheep) but also upon some of very different 

 species, as a sheep and a dog ; the former emitting, the other receiving. 



Note only, that instead of a quill a small crooked thin pipe of silver or brass, 

 so slender that the one end may enter into a quill, and having at the other end 

 that is to enter into the vein and artery a small knob, for the better fastening 

 them to it wiih a thread, will be much fitter than a straight pipe or quill for this 

 operation : for so they are much more easy to be managed. 



