742 THE POPULAR SCIENCE MONTHLY. 



acknowledge the inheritance of physical dispositions, we may consider 

 these frog activities as properties of the central mechanism wrought 

 out during the entire development of the species, and inherited by the 

 given individual." That either of these opinions is more reasonable 

 than the one of Dr, Hammond, I think there can be little doubt, es- 

 pecially after witnessing the experiment performed by Goltz in 1869. 

 Goltz took two frogs and decapitated one and blindfolded the other ; 

 this was done to prevent any voluntary motions that might arise on 

 account of visual impressions. Goltz then placed both animals in a 

 vessel of water and gradually raised the temperature. Both frogs 

 kept quiet until the temperature rose to 25° centigrade ; at this point 

 the frog whose brain was uninjured showed signs of discomfort ; as 

 the heat increased he tried to escape, and died at 42° C. During this 

 entire time the other frog sat perfectly still, and gave no evidences of 

 distress or pain. But — and here is the significant fact — this same ani- 

 mal, while in the water, made all the reflex defensive efforts when 

 acetic acid was applied to the surface. Aside from these activities, it 

 was still, and died at 50° C. If we admit that the mechanism of the 

 cord possesses the possibility of self -regulation, an admission made by 

 Dr. Hammond in the article from which I have quoted, all these phe- 

 nomena may be regarded as simple reflex activities. We may accept 

 Dr. Maudsley's judgment that " the reflex activity of the spinal cord 

 is entirely a physical process, which is nowise prevented from taking 

 place because it is not accompanied by consciousness." 



Anatomy teaches us to exjsect complexity of function as we ascend 

 from the cord to the cerebral hemisphere ; experiment and pathology 

 confirm our expectation. The medulla oblongata, like the cord, con- 

 veys motions to and from the higher centers ; further it is the seat of 

 many reflex activities which are indispensable for the organic processes, 

 and further still, it is, in some of these processes, a self-dependent cen- 

 ter of innervation. I name the more important activities of the me- 

 dulla. This organ is the center for respiration. The excitation of this 

 center is brought about in part automatically by the blood. The 

 decrease of oxygen and accumulation of oxidation products in the 

 blood stimulate this part of the medulla, so that respiratory move- 

 ments may continue after all the afferent nerves connected with the 

 center have been divided. This respiratory mechanism, though truly 

 reflex, is. to a considerable extent, under the control of the will, thus 

 enabling us to articulate for all forms of vocalization. 



The medulla is a center of innervation of the heart. Though the 

 heart will beat if completely severed from the cerebro-spinal system, 

 and, in the case of cold-blooded animals, if removed from the body, 

 still its action is decidedly affected by the fibers which unite it with 

 the medulla. 



Again, the blood-vessels are brought under the control of the me- 

 dulla by the vaso-motor center. The vaso-motor nerves pass by the 



