Excerpt from Heart, Vol. 2: A Journal for the Study of the Circulation; 1910-1911 In some cases tracings were taken from the same dog on successive days but at times when this was attempted it was found that clotting had occurred. This was especially the case when the artery had been much handled. If care is taken in the manipulation of the vessel, tracings may usually be taken on at least three or four successive days. The second method, the most useful in laboratory experiments where a single observation is required, was a slight modification of the first method. In a preliminary aseptic Operation under ether the left carotid artery was isolated for several inches and brought up close under the skin and the wound closed. On the following day, or after recovery from the anaesthetic, an ordinary three-way cannula was tied into the artery and the blood-pressure taken in the usual way. (in order to avoid all possibility of causing the slightest pain, cocaine may be applied locally during this part of the work but it is not necessary, for the animals Show no evidence of pain even when cocaine is not used.) By this method only one observation from each animal can be obtained. The third method consisted in the use of a trocar cannula (fig. This method is the most useful where brief and successive observations are to be made for a number of days, or especially where it is desirable to use different arteries of the same animal. For example, this method might be employed in determining from day to day the changes in blood-pressure in a dog subjected to experimental nephritis or it might also be employed in comparing Simultaneous blood-pressure tracings taken from several different arteries of the same animal. Bardier2 has invented a trocar cannula for blood-pressure work, but it is not adapted for use upon the intact animal. Our trocar cannula is made of steel. It is used by first inserting the instrument with the obturator in position, after which the obturator is entirely removed, leaving the end of the cannula within the lumen of the blood-vessel. The other end of the cannula is connected by a rubber tube with the manometer and pressure bottle. A segment from the distal end of this rubber tube in connection with the trocar cannula is shown in Fig. 2. The bristle which is shown in the drawing is not used, of course. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.