2 1 6 Life and Health 



transmitting sensory and motor impressions from the cord 

 to the brain and return. 



The medulla is also the seat of a number of reflex centers 

 connected with the influence of the nervous system on the 

 blood vessels, the movements of the heart, respiration, 

 swallowing, and the secretion of saliva. 



In the medulla also are centers for coughing, vomiting, 

 swallowing, and the dilation of the pupil of the eye. It is 

 also in part the deep origin of important cranial nerves. 



Experiment 94. To show the brain. A sheep's or calf's brain is 

 to be preferred, on account of its larger size. Get one fresh from the 

 butcher. Pay him to dissect away the skin and muscles of the skull, 

 under your direction, and to saw open the cranium in a circular direc- 

 tion. Take time, and remove the sawed top with great care, tearing 

 away the dura mater from the bones. 



Now cut away enough of this membrane so that the sides of the 

 skull can be sawed and torn away, to allow us to lift out the brain, 

 with proper dissection, in as perfect a state as need be. Put all the 

 torn parts and membranes back into place. 



Note the dura mater, the arachnoid lining it, and the pia mater 

 closely attached to the brain. Find the cerebrum, or big brain, the 

 cerebellum, or little brain, the medulla, and the stumps of the cranial 

 nerves, especially the stumps of the optic nerves. The brain should 

 be first examined as a whole, and compared with the description 

 given in the text, or the pictures of the human brain. 1 



NOTE. A fresh brain is too soft for handling or for careful study. 

 Hence it should be hardened and made ready for use several weeks 

 before it is needed for class use. A mixture of \ ounce of bichromate 

 of potash and i ounce of a 40 per cent solution of formalin to about 

 I quart of water makes a useful hardening and preserving fluid. A 

 mixture of two-thirds strong alcohol and one-third 2 per cent solution 

 of formalin is also recommended. 



1 Space does not allow us to give in necessary detail the directions for 

 the experimental study of the brain. Such directions are admirably given 

 in Brown's Physiology for the Laboratory, a book already referred to on 

 page 20. 



