608 



SCIENCE 



[Vol. LV, No. 1432 



tal, one day a new patient aj)proaehed my desk 

 just as I was about to sign a letter. The mo- 

 ment I looked up at him I was struck with his 

 appearance and instantly said to myself, 

 "Surely you are Dalton's cat." "Where were 

 you wounded?" I quickly asked. He pointed 

 to his neck and I said to myself, "His sjnnpa- 

 thetie nerve must have been cut." Further 

 careful observation showed the reddened ear, 

 the increased temperature, the sweating and 

 the greater flow of saliva, thus confirming in 

 every particular the results of Brown-Sequard's 

 experiments on animals. It is interesting to 

 know that this was the very first ease in sur- 

 gical history in which division of the sympa- 

 thetic nerve had ever been observed in man. 



Further experiments on this little nerve in 

 animals revealed a wholly new world of most 

 important phenomena. It was discovered that 

 the sympathetic nerve sent branches to every 

 artery in the body, from head to foot. Now 

 the arteries are tubes, like the water pipes in a 

 house, not, however, of rigid metal hut soft 

 and flexible, for they consist largely of mus- 

 cular fibers which contract or relax automat- 

 ically, making the arterial tubes of a larger or 

 a smaller diameter according to the need for 

 more or less blood. 



For instance, just before a meal, the stomach 

 is of a yellowish color. Not a single blood 

 vessel is to be seen. An hour later the stomach 

 has become so red that it seems almost as if 

 the wall of the stomach is made up of nothing 

 but blood vessels. This greatly increased sup- 

 ply of blood is needed to secrete gastric juice 

 for the digestion of our food. As the food is 

 digested, less and less blood is needed, the 

 caliber of the arteries is gradually duninished 

 by the contraction of the muscular wall of the 

 arteries until the stomach looks as bloodless as 

 before .breakfast. 



How fortunate that all this is automatic! 

 Were it not, and after breakfast you forgot to 

 order an increasing supply of blood for diges- 

 tion, or if after digestion was accomplished, 

 you forgot to shut off the blood, what would 

 become of you? 



The iris, the colored circular curtain inside 

 the eye, with a round, black hole in the center 

 called the pupil, is under similar automatic 



control of this sympathetic nerve. The iris is 

 like a wheel. Around the pupil there are eii'- 

 cular fibers which one may call the hub, while 

 the rest of the iris consists of radiating fibers 

 corresponding to the spokes. When you go 

 out of doors, the bright light at first almost 

 blinds you, but very quickly the circular fibers 

 around the pupil contract so that the pupil 

 becomes as small as a pin hole and protects 

 the retina. On going into a dark room, at first 

 you stumble over the furniture, but in a few- 

 moments the radiating fibers pull the pupil 

 wide open and you see clearly everything in 

 the room. 



When you blush from emotion, the arteries 

 of your skin have dilated. When you turn 

 pale with fright, the caliber of your arteries is 

 lessened, and if the arteries going to your brain 

 supply too little blood, you fall in a faint. 

 When you cut your hand, j'ou know how all 

 around the cut the redness shows that the arte- 

 ries have dilated to furnish extra blood for the 

 repair of the injury, and when the wound is 

 healed, your blood vessels again contract and 

 the redness at last disappears. 



All these processes also are automatic. You 

 do not have to remember to order blood to or 

 from a cut hand, or to contract or widen the 

 pupil, etc. It is all done for you; in fact, it is 

 done in spite of j'ou, for you have not the least 

 control over these varying conditions. The 

 automatic action of this nerve is of the utmost 

 importance for many functions involving life 

 itself. 



I could go on almost indefinitely with a multi- 

 tude of similar illustrations. All of our knowl- 

 edge of these facts started from Brown- 

 Seciuard's little experiment of cutting the 

 slender sjonpathetic nerve in the neck of an 

 animal. 



VII. Another evidence of our anmial origin 

 is found in organs which are well developed and 

 aetivelj' functioning in some of the lower ani- 

 mals, but which in man are only rudimentary. 

 The best known example of this is the appen- 

 dix, which, in some of the lower animals, is 

 well developed and functions actively. Its fz-e- 

 queijt inflammation is also a good example of 

 the fact that such imperfect vestigial organs 

 are very prone to disease and often require the 



