UPON THE VASCULAR SYSTEM. 



137 



means so inactive as their discoverers have concluded, from the small number 

 of experiments performed by them. Seeing, therefore, that these nerves are 

 not unfrequently in action, and seeing that in the dog, as above stated, the 

 trunks of the vagi cannot be divided without at the same time cutting across 

 the depressor nerves, I am compelled to admit that, in the group of experiments 

 on dogs just given, the increased blood-pressure which followed section of the 

 vagi may have resulted from section of the depressor nerves, and from these 

 only. The question at issue must therefore be decided by experiments on cats 

 and rabbits, seeing that in these animals the superior cardiac branch (depressor 

 nerve) leaves the vagus high in the neck, and can therefore be divided sepa- 

 rately from the trunk of the latter.* If, however, the results of the foregoing 

 experiments on dogs were due to the action of the depressor nerves, then we 

 should require to adopt the conclusion that these nerves act during digestion, 

 and are inactive during fasting. Such a conclusion is opposed by the results of 

 experiments on rabbits and cats, which are yet to be detailed. There is no 

 evidence whatever that the depressor nerve acts more during digestion than 

 during fasting ; and therefore, after all, these experiments on dogs really do 

 support the idea that during digestion vaso-inhibitory fibres, distinct from the 

 " depressor " nerve fibres, in the vagus are thrown in action. 



The following experiments on rabbits and cats are, however, entirely free 

 from the source of fallacy that obtains in the case of dogs, because in the 

 former animals the nervi-depressores can be divided without the vagi being at 

 the same time implicated. 



B. EXPERIMENTS ON EABBITS AND CATS, 

 (a.) During Digestion. 



Carclio-inhibitory Nerves paralysed by Atropia. 



EXPEBIMENT XXXIX. — Strong Babbit fed at 2 p.m. Canula in Carotid Artery. 



Trachea open. 



Time. 



Pulse in 10". 



Mean Pressure in inches 

 ofHg. 



General Notes. 



3-57' 



44 



4 





59' 







10 milligrammes atropiae sulph. 

 injected into vein. 



30" 



44 



4-5 





4" 1' 







Both depressors divided. 



30" 



40 



4-4 





2' 







Both vagi divided. 



3' 



39 



5-5 





4' 15" 



38 



5-3 





6' 20" 



38 



5-2 





10' 



39 



53 





* The reader -will now understand why remarks on the blood-pressure were omitted from the 

 commentary on the first group of experiments on dogs (see page 122). 



