THE EARLY DAYS OF COMPARATIVE ANATOMY. 169 



of vessels, is satisfactorily dealt with, but the investiga- 

 tion of the heart involves them in unexpected confusion. 

 They are of course aware that the Seal is not a fish, and 

 cannot breathe under water. They are also aware that 

 in the Mammalian foetus blood is diverted from the right 

 side of the heart to the left through the foramen ovale 

 in order to avoid the lungs, and they draw from this the 

 fatal conclusion that the foetus does not respire. They 

 profess to have found, and, indeed, may actually have 

 found, a persisting foramen ovale in the heart of the Seal, 

 and they believe that when the animal dives, and remains 

 some time below water, the circulation follows the same 

 course as in the intra-uterine embryo. The fact that the 

 Seal is only below water for a relatively short time, whilst 

 the circulation in the foetus remains the same through- 

 out foetal life, should have warned them of the risk of 

 assuming an interruption in the normal circulation every 

 time the breathing organs were cut off from the atmos- 

 phere. 



The Parisians describe for the first time in the 

 Barbary Cow the valves in the primary hepatic branches 

 of the portal vein, which are correctly interpreted as 

 preventing the reflux of blood into the parent vein. 

 These valves are not present in man. But a still more 

 remarkable vascular phenomenon is discussed in the 

 Stag, where the external and internal jugular veins are 

 stated to possess sixteen valves disposed in six rows, the 

 cavities of the valves being directed, not towards the 

 heart, but towards the head. They fully recognise the 

 unusual and incredible nature of this arrangement, 

 which is explained as preventing "the too great 

 impetuositie of the bloud which falls in its returne from 

 the brain into the axillary branches." I am not aware 

 that this statement has ever been confirmed or denied, and 



