154 M CIRCULATION OF THE BLOOD AND LYMPH 



of pleurisy with effusion. It is to be remarked, however, that 

 although beats of a kind can be obtained a long time after death, 

 they are either confined to the auricles or to portions of them, or, 

 if they involve the ventricles too, they are only shallow and local 

 contractions, especially seen in the neighbourhood of the larger 

 coronary vessels, and are utterly inadequate to the maintenance 

 of an efficient circulation. The heart can also be resuscitated in situ 

 for some time after complete stoppage without the injection of any 

 solution by clamping the aorta in the thorax and practising direct 

 cardiac massage, the lower end of the animal at the same time being 

 elevated to allow blood to pass out of the engorged abdominal veins 

 to the right auricle. The clamping of the aorta permits a sufficient 

 pressure to be attained for the filling of the coronary arteries. The 

 injection of adrenalin into the blood has also been recommended as 

 a means of raising the blood-pressure by constricting the small 

 arteries, and stimulating the action of the cardiac muscle. The 

 possibility of restoration of the mammalian heart many hours after 

 somatic death has been considered by some a strong argument for 

 the myogenic theory of cardiac automatism, since, they say, it is 

 improbable that ganglion-cells, elsewhere such physiologically 

 fragile structures, should in the heart retain their vitality for so 

 long a time. But it is easy to overdo this argument, and we must 

 not assume without proof that ganglion-cells in all parts of the body 

 have an equal capacity of survival. Indeed, we know that there 

 are great differences, the nervous mechanism concerned in respira- 

 tion, e.g., being capable of restoration when the circulation is re- 

 newed after total anaemia of the brain and cervical cord lasting for 

 as much as an hour (in cats), while the nervous mechanism con- 

 cerned in voluntary movements cannot be completely restored even 

 after a much shorter interval. It is very probable that the cardiac 

 ganglia, if the all-important automatic function of the heart depends 

 upon them, are, like the cardiac muscle, endowed with exceptional 

 powers of resistance to those changes which constitute death. 

 The possibility also must not be overlooked that the contractions 

 obtained after such long intervals are not truly automatic, but 

 similar rather to the rhythmical beats developed under the influence 

 of pressure in the frog's apex preparation or by immersion in salt 

 solutions of tortoise ventricle strips. 



In addition to its marked power of rhythmical contraction, the 

 cardiac muscle is distinguished from ordinary skeletal muscle by 

 other peculiarities. It used to be considered the most striking of 

 these peculiarities that ' it is everything or nothing with the heart ' ; 

 in other words, that the heart muscle, when it contracts, makes the 

 best effort of which it is capable at the time; a weak stimulus, if 

 it can just produce a beat, causing as great a contraction as a strong 

 stimulus. Recent work, however, has indicated that this property 



