470 GROWTH OF BIOLOGY IN THE NINETEENTH CENTURY. 



effectiveness^ Or what should the victims of science, so trifling in 

 number, signify in compurison with the numberless and much more 

 grievous sufferings which in the unalterable order of nature one animal 

 often inflicts upon another, it may be in bestial cruelty, or in com- 

 parison with the pain Avhich the human race endures from accidents 

 and diseases of all kinds, or which men inflict upon one another in 

 nmi'dci-ous wars? 



People ought rather to be thankful that by experiments upon 

 animals physiology has in the nineteenth century most successfully 

 increased the the treasure of our knowlcMlge. The section and excita- 

 tion of the spinal roots brought us Hell's theorem. In the same way 

 the physiology of the most various peripheral nerves was brought into 

 existence, including that most importiuit of all this series of doctrines, 

 that of the action oi the vagus nerves. Johannes Miiller established the 

 law of the the specific energy of the nerves of sense. Partial sections 

 of the spinal cord and the study of the heightened and lowered degen- 

 eration thereby produced enabled us to get a view of the different 

 nervous paths of conduction. Acute experimenters even succeeded in 

 penetrating into the secrets of the functions of the brain b}'^ localized 

 lesions, by removal or other destruction of particular parts of the 

 brain, and in discovering in the spinal marrow a special center of 

 breathing and vascular control, in particular places of the cortex, here 

 a center of language, there a seeing tract, a hearing tract, or a feeling 

 tract, etc. 



Experiments upon animals have put many other departments of 

 physiology within reach of the scientific understanding. The cele- 

 brated Harvey's doctrine w^as refined to a mechanics of the circulation 

 of the blood when the velocity of the current, as well as its pressure 

 in different parts of the system of tubes, had been accurately measured 

 b}- ingenious devices. The study of the physiology of digestion and 

 of metabolism was well begun Ity making fistulas into the stomach 

 and intestines or by otherwise ol)taining juices of the different glands, 

 and these, once obtained, were made the subjects of further experi- 

 ments to discover their functions in the process of digestion. 



A still greater blessing for mankind has come from experiments 

 upon animals in two other directions, which in the nineteenth century 

 have been systematicall}^ prosecuted and which are intimately con- 

 nected with practical medicine, but do not require vivisection. One 

 direction is that of the study of the effects of chemical bodies upon the 

 organism into which they are absorbed. The investigator ought first 

 to ascertain by numerous sj^stematically conducted experiments upon 

 animals what effects in every part of the system chloroform and ether, 

 morphine, cocaine, antipyrine, or powerful poisons such as atropin, 

 belladonna, strychnine, curare, and numerous other chemicals which 

 chemical manufacturers are throwing in constantly increasing profu- 



