182 Frogs and their Contributions to Sri, nee. 



foetus, and the last to disappear upon death. Kadi Sanc- 

 tion we have mentioned has it- diastaltic arc as it is <•; lied, 

 that is, a aerve famishing tin- way <>r commanicatioa from 

 the surface to the centre, which would be the cord and its 

 extension the medulla oblongata ami a nerve from the 

 centre communicating t<» tin- surface. For instance, the 

 presence of carbonic acid in the capillaries of the lung 

 stimulates the fibres of the pneamogastric nerve, and 

 gently says, I want more oxygen. The message travel to 

 the centre, and the response comes back along different 

 nerves to the muscles of the back, the intercostal mus. 

 and the diaphragm. The cavity of the thorax widens and 

 air rushes in. Now it is only by knowledge of the true 

 physiology of functions that we can rightly or rationally 

 proceed to restore them if disordered. It becomes, there- 

 fore, a practical and all important matter in the treatment 

 of disease to know just how far we are permitted to lift 

 the veil that hides its true locality and nature, as well as 

 to know the true and proper direction in which to bend 

 our efforts and address our remedies. Since the promul- 

 gation of Marshall Hall's discovery, the diagnosis of di- 

 seases has been greatly sharpened, and the practice of medi- 

 cine simplified and rationalized. The law of diastaltic 

 action is to the medical world what gravity is to the physical. 

 If we have spoken of it at tedious length, its importance 

 and the application we wish to make of it must be our 

 excuse. That application is simply this: that the disco- 

 very was suggested to Dr. Hall's mind by witnessing the 

 automatic motions of decapitated frogs and newts, and 

 elucidated by a systematic series of experiments upon these 

 and other animals, hut especially upon frogs, by reason of • 

 the facility with which they could be procured, and the 

 peculiar BUSCeptibility of their nervous system. 



We do not claim for frogs, that they were the instru- 

 ments ushering in Harvey's great discovery of the circula- 



