FUNCTIONS OF THE CEREBRUM. 597 



were, in the main, confirmed, except as regards the special senses. Bouillaud, in 1826, 

 made a large number of observations upon pigeons, fowls, rabbits, etc., in which, after 

 removal of the hemispheres, he noted the persistence of the senses of sight and hearing. 

 Longet finally demonstrated the fact that both sight and hearing are retained after extir- 

 pation of the hemispheres, even more clearly than Bouillaud, by the following experi- 

 ments : He removed the hemispheres from a pigeon, the animal surviving the operation 

 eighteen days. When this animal was placed in a dark room and a light was suddenly 

 brought near the eyes, the iris contracted and the animal winked ; "but it was remark- 

 able, that when a lighted candle was moved in a circle, and at a sufficient distance, so 

 that there should be no sensation of heat, the pigeon executed an analogous movement 

 of the head." An examination after death showed that the removal of the cerebrum 

 had been complete. An animal deprived of the hemispheres also opened the eyes at the 

 report of a pistol and gave other evidence that the sense of hearing was retained. 



With regard to the senses of smell and taste, it is more difficult to determine their 

 presence than to ascertain that the senses of sight and hearing are retained. It is prob- 

 able, however, that the sense of smell is not abolished, if the hemispheres be carefully 

 removed, leaving the olfactory ganglia intact ; and there is no direct evidence that extir- 

 pation of the cerebrum affects the sense of taste ; indeed, in young cats and dogs, Longet 

 has noted evidences of a disagreeable impression following the introduction of a concen- 

 trated solution of colocynth into the mouth, as distinctly as in the same animals under 

 normal conditions. 



We shall now proceed to describe, as accurately as possible, the condition of an ani- 

 mal after complete extirpation of the cerebrum, as observed in numerous experiments 

 that we have ourselves made upon this subject, premising the statement that these are 

 merely repetitions of observations made by other physiologists. 



A pigeon, in a perfectly normal condition, is deprived of the hemispheres, by remov- 

 ing the calvarium and carefully scooping out the parts with the handle of a scalpel. 

 This operation is usually not difficult, and the haemorrhage is soon arrested spon- 

 taneously. The slit in the scalp is closed with sutures, and the animal is set at liber- 

 ty. The appearance of the animal after this mutilation is peculiar and characteristic. 

 There immediately supervenes a condition of stupor. There is usually no attempt at 

 movement, and, though the pigeon stands upon its feet, the head is almost buried in the 

 feathers of the neck, the eyes are closed, and the attitude is one of absolute indifference 

 to surrounding conditions. The muscles seem to act with just sufficient vigor to main- 

 tain the standing position. If we pinch one of the toes or grasp the beak, there is evi- 

 dent sensation, and a persistent and more or less vigorous effort is made to release the 

 part. It is sufficiently evident, from these and other tests, that sensation and the power 

 of voluntary motion are retained ; but, as soon as the animal is left quiet, it relapses into 

 its stupid condition, makes no effort to escape, and apparently loses immediately all 

 recollection of having been disturbed. The irritation has evidently produced a sensation 

 of discomfort and has given rise to a voluntary muscular effort ; but there has been no 

 idea of danger, nor an intelligent effort to avoid a repetition of the disagreeable or pain- 

 ful impression. 



It is easy to demonstrate, by experiments such as we have just detailed, that the 

 animal sees and hears ; but it connects no idea with any thing seen, and the report of a 

 pistol, which, under natural conditions, would excite terror and an idea of danger, simply 

 causes the pigeon to give evidence that the sound has been heard. As we have already 

 stated, it is probable that the animal has the sense of smell, but it is difficult, if not impos- 

 sible, to establish this point experimentally. The same remark applies to the sensations of 

 hunger and thirst. The animal may feel the want of water and food, but it has no idea of 

 relieving these sensations by drinking and eating, and, if left to itself, will die of inanition. 



Tli ere has been a great deal of discussion among experimentalists with regard to 

 spontaneous voluntary movements in animals deprived of the cerebral hemispheres. The 



