It is nevertheless essential to assure oneself during the whole progress of an anæsthesia that the circulation is in a satisfactory condition. Two obvious guides to this are the colour of the patient’s face and the force with which cut arteries spout. As regards the colour in circulatory failure, one would naturally expect a pallid face, and this indeed is the rule. It must not be forgotten, however, _that cyanosis may sometimes be cardiac in origin_. Cases do sometimes occur when a bluish tinge is seen on the lips, ears, and nostrils, apart from any obvious cause of oxygen starvation. In these we may reasonably suspect that the right heart is failing, and take measures accordingly. Another valuable index to the state of the circulation is the “skin reflex,” that is, the speed with which the circulation returns to an area of the skin which has been pinched. The student should train his eye by occasionally pinching the lobule of the patient’s ear and observing first the white area so produced, and later the rate at which, in a normal case, the healthy colour returns. Abnormal Phenomena in Anæsthesia. It is not intended to furnish here any account of matters more suitably treated under the “Accidents of Anæsthesia,” which are fully described in Chapter xvi., but merely to draw the attention of the student to certain departures from the normal course of anæsthesia which are encountered with varying frequency, to ascribe them as far as possible to their true causation, and indicate methods of prevention. The abnormalities fall into two classes, those connected with the nervous and muscular systems, and those in which respiratory changes are evident. MOTOR AND NERVOUS SYSTEM. _Clonus or tremor_ sometimes appears in one or more limbs, even the trunk being affected in severe cases. Ether is practically the only anæsthetic under which the tremor ever appears, and the condition is often spoken of as “ether tremor.” It rarely appears in the female subject, being almost limited to powerfully built young men. Coming on towards the end of the second stage, it frequently persists in the deepest of third stages, and in bad cases there is usually no option but to change over to chloroform--always supposing that the tremor will interfere with the work of the surgeon. If it will not, the condition calls for no active treatment, since it is in itself not dangerous.