June 9, 1905.] 



SCIENCE. 



889 



be got. Defibrinated blood was found to 

 be better than Locke 's solution. 



The Nature of Cardiac Inhibition, ivith 

 Special Beference to the Heart of Lim- 

 ulus: A. J. Carlson. 

 It is commonly believed to-day that the 

 cardio-iuhibitory nerve-fibers act directly 

 on the heart muscle. This view is a corol- 

 lary of the myogenic theory of the nature 

 of the heart-beat. In Limulus the heart 

 beat is neurogenic. The cardio-inliibitory 

 nerves act on the local heart ganglion in a 

 way to stop or diminish its activity and do 

 not act directly on the heart muscle. This 

 conclusion rests on the following evidence : 



(1) stimulation of the nerves that pass from 

 the cardiac ganglion to the heart muscle 

 produces motor and not inhibitory effects; 



(2) the diminution of the excitability of 

 the heart during complete inhibition is the 

 same as after extirpation of the heart 

 ganglion; total inhibition thus amounts to 

 throwing the ganglion out of function; (3) 

 atropin paralyzes the eardio-inhibitory 

 nerves only in case it comes in contact with 

 the heart ganglion, but not if it comes in 

 contact with the heart muscle and the 

 nerves passing from the ganglion to the 

 heart muscle. 



Weber's theory of the nature of the 

 cardiac inhibition is thus shown to be true 

 for the Limulus heart. Stimulation of 

 cardio-inhibitory nerves in Limulus pro- 

 duces the same effects as those produced in 

 the vertebrate heart by stimulation of the 

 vagi. The mechanism of cardiac inhibition 

 in vertebrates probably does not differ 

 from that in Limulus, as all the changes 

 produced in the heart by the stimulation of 

 the vagi can be accounted for on Weber's 

 theory. Cardiac inhibition is, therefore, to 

 be referred to the category of inhibitory 

 processes known to take place in the central 

 nervous system, that is, the inhibition of 

 one neural process by another. 



Effects of Simultaneous Section of BotJi 

 Vagi above the Origin of the Recurrent 

 Laryngeal: G. N. Stewart. 



1. At the Madrid International Congress 

 of Medicine (April, 1903) Ocana showed a 

 dog which, ten weeks after this operation, 

 was in perfect health. It remained so for 

 more than six months. He supposes that 

 this was the first instance of such a result. 

 In November, 1900,* however I described 

 similar cases. In February, 1897, a dog 

 was operated on, which lived in excellent 

 health for many months. An account of 

 this animal was sent on March 31, 1897, to 

 a friend for insertion in an eastern medical 

 journal, but was not considered suitable. 

 At the autopsy I found the two portions of 

 the left vagus still separated by a wide in- 

 terval. In the right vagus such perfect 

 union had taken place that only a fine 

 linear scar remained, barely visible to the 

 eye, but easily recognizable with the aid of 

 a hand lens, and still better on microscop- 

 ical examination of longitudinal sections. 

 Such instances of perfect recovery and long 

 survival are quite rare, at least in this 

 climate (two, or at most three, cases out of 

 sixty dogs, in my experience). Whether 

 they are to be explained by some anomaly 

 in the distribution of vagus fibers, or by 

 some happy ' conjunction of circumstances, ' 

 which enables the animal to survive the 

 critical period, or, what seems less likely, 

 by an abnormally rapid regeneration or 

 partial regeneration of one of the nerves, 

 must be left undecided. 



2. In all dogs (including these excep- 

 tional cases) after double vagotomy the 

 ratio, pulse rate to respiratory rate is much 

 increased (before operation, 3:1 to 5:1; 

 after operation, 9:1 to 40:1). If the ani- 

 mals live for more than a few days the ratio 

 tends to diminish somewhat through slow- 

 ing of the pulse. The rate of respiration, 



* ' American Yearbook of Medicine,' 1901, p. 

 548. 



