598 
DE. PAVT OX SrOAE E0E:MATI0X IX THE LITEE. 
with the freedom of the breathing. In resorting to catheterism of the heart, my expe- 
rience is, that unless the animal has remained perfectly tranquil during the whole of 
the operation, the blood will give a decidedly stronger shade of sacchai'ine indication 
than is obtained under a natural or tranquil state of the system. 
According to the state of tranquillity or restlessness of the animal, I can predicate with 
confidence the condition its blood will present ; and when the operation is unattended 
with the least attempt at resistance, \vhich only happens occasionally, the amoimt of 
reaction is so small that it is liable to be overlooked altogether, unless special attention 
is given. It is for this reason that I can reckon with greater certainty on meeting with 
the blood of the right side of the heart in a perfectly normal state on suddenly killing the 
animal and instantly excising the heart, than on removal through the catheter dming life. 
This affords an explanation, why blood removed from the carotid artery immedi- 
ately after exposing the vessel, is ordinarily found in a marked degree more sacchaiine 
than when collected ten minutes or so after the operation of exposing the artery- has 
been effected. From the contiguity of the carotid artery to the pneumogastric nerve, 
picking up the vessel is almost universally attended with considerable struggling and 
disturbance of the breathing. But when the artery has been once fully separated from 
its adjacent structures and a ligature placed aromid it, it can be drawn out and blood 
collected without causing any fresh struggling or disturbance. 
I have upon a few occasions found blood removed from the carotid artery giAing a 
shade stronger reaction than the blood prewously withdrawn from the right side of the 
heart. I consider this to have been due to the different effects of the respective opera- 
tions required. Exposing the jugular and passing a catheter into the heart, is not so 
likely to occasion struggling and disturbance as exposing the carotid. 
From some experiments I have recently performed, it would seem that the portal 
blood, instead of being entirely free from sugar, contains, as far as is discoverable by the 
behaviour of the blue liquid, the same amount that is met with under natural circum- 
stances in the heart and other parts of the circulatory system. Blood is examined 
(certainly by myself) much more closely now, than when such a wide difference was 
considered to exist in it from different parts of the circulation. A trace of reaction is 
now looked for and noted that w'ould have formerly passed over unobserved. For 
instance, on well-boiling a specimen derived from portal blood with the blue liquid, 
there is no reduction to be perceived. The test appears to have given no reaction, and 
such would have been formerly described as the result. Had the test-tube been placed 
aside, however, and examined again in the course of half an hour, just a traceable 
amount of red oxide would have been found, according to my recent experience, to have 
subsided. The following is the account of three consecutive experiments that I have 
lately performed, in which a careful comparative examination of the portal and cardiac 
blood was made. The dogs had been feeding on tripe for some days past. They were 
suddenly killed by pithing. The abdomen being instantly opened, a ligatm'e was placed 
(observing the precautions mentioned by Berjn'aed) around the portal vein. The chest 
