BIOLOGY. 295 



and semi-voluntary muscular mechanism is also not involved ex- 

 cept when extreme and fatal symptoms are developed. What 

 parts, then, are influenced by an anaesthetic? The idea was 

 almost intuitive that the brain was the organ affected, and that 

 the centres of consciousness are those chiefly held in abeyance. 

 But, to prove this as true, experiment was necessary. In proof. 

 Dr. Richardson took a large pigeon, narcotized it deeply with 

 chloroform, and in this state passed through its body, from the 

 head to the foot, a rapid intermittent induction current. The bird 

 instantly rose from the table, extended its wings, opened its eyes, 

 and seemed as if restored ; the current was then stopped, and the 

 bird was shown to be as deeply asleep and as powerless as before. 

 Another bird was put to sleep by freezing the brain, and when 

 utterly insensible was subjected to the electrical shock in the satne 

 way, when it flew from the table into the room, where, bi'eaking 

 its connection with the battery, it dropped on the floor comatose, 

 motionless, and as anaesthetized as before, in which condition it 

 remained for many minutes. 



These experiments demonstrated that the anaesthetic action was 

 localized in the cerebrum. His battery was like an outer brain, 

 which supplied power without intelligence, and which, by the 

 effects of its currents, showed that all the muscular elements were 

 ready for work, and only awaited the order from the brain. What, 

 during the process of anaesthesia, leads to this change in the 

 brain ? Is there a chemical action on albumen ? Is there pres- 

 sure on brain matter .f^ Is there deficient oxidation of the 

 blood .f* Is there contraction of blood-vessels, and diminished 

 supply of blood from that cause ? All these hypotheses were 

 experimentally tested and negatived. It was admitted that 

 during extreme anassthesia there is reduced oxidation and a sin- 

 gular reduction of temperature. These changes are inevitable, 

 because the anaesthetic vapors replace ox3^gen during their diffu- 

 sion into blood; but the diminished oxidation is not the cause of 

 the insensibility. In proof of this, Dr. Richardson showed an 

 animal breathing an air in which the oxygen was reduced by 

 addition of nitrogen from 21 parts to 9 parts in the 100, side by 

 side with another similar animal breathing an air in which the 

 oxygen was reduced by the addition of vapor of bichloride of metli- 

 ylene only to about 20 parts in the 100 ; namely, 4: cubic inches in 

 500. The result was that the animal in the extremely reduced atmos- 

 phere was quite unaffected, while the animal in the slightly reduced 

 atmosphere was in the deepest narcotism. Then a correcting ex- 

 perimental test was adopted, and the bichloride was administered 

 in an atmosphere containing an excess of oxygen, the oxygen 

 being present in double its ordinary or natural proportion ; the ex- 

 cess of oxygen exerted no perceptible obstacle to the anassthesia. 



To determine whether there was contraction of blood-vessels 

 under anaesthetics, he had recourse to transparent small trout ; 

 through their bodies, with the microscope and the inch lens, the 

 blood-vessels could be seen, and the corpuscles flowing through 

 them. These animals can be narcotized readily by making iheni 

 breathe water saturated with chloride of methylene or ether. In 



