Walter Ilolbrook Gaskell. 



XXIX 



muscle cell to the next without the intervention of nerve fibres. In 1875 

 he advocated a similar view as regards the passage of contraction from 

 one part of the ventricle of the frog's heart to the rest, and he thought 

 this was probably also the case in the auricle. But in one important point 

 he kept to the old theory and considered that the passage of contraction 

 from auricle to ventricle was brought about by nerve cells and nerve fibres. 

 Gaskell (1881) at first adopted the current theory with some modifications in 

 detail, but in 1883 he abandoned it, and argued that the contraction of the 

 heart was of muscular origin ; it started in the sinus and spread as a 

 peristaltic wave to the other chambers, the delay in the passage of the 

 contraction wave from one chamber of the heart to the next being due to 

 a slow conduction in the modified muscular tissue which he found at the 

 junction of the sinus venosus with the auricle, and at the junction of the 

 auricle with the ventricle. In the course of his work Gaskell made a large 

 number of original observations on the behaviour of the several parts of the 

 heart and of the cardiac muscle. The term " block " Gaskell adopted from 

 Romanes' account of the passage of contraction waves in Medusae ; the pheno- 

 mena had been partly worked out in the frog's ventricle by Engelmann, but 

 they were much more completely elucidated by Gaskell's work on the heart of 

 the frog and the tortoise. It was known that the contraction of the ventricle 

 might only occur at every second, third, or fourth beat of the auricle. Gaskell 

 obtained this effect experimentally by varying the degree of block between 

 the two chambers. After the lapse of years the invention of the string 

 galvanometer brought the observation of heart block in man into the region 

 of clinical medicine. 



The different effects produced on the heart of the frog by stimulating the 

 vagus nerve were investigated simultaneously by Gaskell and by Heidenhain. 

 Gaskell observed that stimulation of the vagus sometimes caused an increase 

 in the strength of the beats in addition to the quickening which had been 

 already described by Schmiedeberg and others, and which had been 

 attributed to special accelerator nerve fibres. Heidenhain found that by 

 stimulating the medulla oblongata at different points, acceleration and 

 augmentation, or slowing and weakening, of the heart beat could be obtained. 

 Gaskell traced in the crocodile and frog; the origin of the accelerator 

 fibres to the sympathetic system, and this was followed up by a more 

 complete anatomical investigation by Gaskell and Gadow. The innervation 

 of the heart of lower vertebrates was thus brought into line with that 

 of the mammal. In addition, he gave a more complete account than 

 had been given by Heidenhain of the cause of the independence of the 

 slowing and the weakening of the heart beat caused by pure vagus fibres, 

 and of the quickening and the increase of strength caused by sympathetic 

 fibres. A little later Gaskell showed that an electrical change can be 

 produced in quiescent heart muscle on stimulation of the cardiac nerves, and 

 that the change is different according as the vagus or the accelerator nerve 

 is stimulated. 



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