_Movements recalling to the observer the condition of athetosis seen in the limbs of hemiplegics_ are occasionally seen in the anæsthetised patient. The fingers of a hand may be slowly moved, or one or other shoulder may be shrugged. The exact cause of these movements is obscure. They occur in all types, both sexes, and at all ages; they are not necessarily asphyxia though a trace of asphyxia seems sometimes to conduce to them. They persist for some time after the third stage has been entered, and ultimately disappear without any obvious cause other than the passage of time. It is rare for them to continue more than five or ten minutes after full anæsthesia has been induced. Their practical importance lies purely in this, that the inexperienced anæsthetist observing some muscular movements still persisting, may take them as an infallible sign that anæsthesia is not complete, and may deliberately take his patient to a deeper level. If in doubt, the anæsthetist must, of course, consult all the other recognised guides, such as the eye reflexes, but once he has seen these movements in a case, and had demonstrated to him _their slow, rhythmical character_, he is not likely to be misled on a future occasion. _Muscular rigidity_ has been mentioned already in Chapter iii. When it persists in a patient in whom other signs suggest that a full anæsthesia has been produced, the anæsthetist will usually find that attention to the air-way, and perhaps a whiff of oxygen, will remedy the trouble. Respiratory Abnormalities. _Shallow breathing_ or even slight temporary arrests of respiration arise frequently. During the induction stage they may be due to:-- 1. Apnœa or acapnia following voluntary excessive breathing. 2. Using morphia before chloroform. At a later stage, it may be due to:-- 1. Acapnia following excessive breathing excited reflexly from the seat of operation. 2. Direct reflex inhibition of the respiratory centre. An example of this is seen sometimes when the bladder is over-distended by lotion. 3. Impending vomiting.