264 PHYSIOLOGY CHAP. 



the investigations of Kronecker and Stanley-Hall, quoted on p. 21 

 (Fig. 13). 



Baglioni showed in a preliminary series of researches (1900), 

 carried out especially upon the spinal cord of the frog, that it is 

 possible to differentiate between the individual elements of the 

 central substance by their reactions to certain poisons. He started 

 from the observation that strychnine and phenol have the common 

 property of increasing the reflex excitability of the spinal cord to 

 an enormous extent, but the disturbances they produce are dis- 

 tinct. While strychnine poisoning causes tetanic spasms in all the 

 muscles of the body so that co-ordinate movements become im- 

 possible, phenol poisoning does not abolish co-ordinated movements, 

 but these are interrupted by rapid clonic contractions which produce 

 constant attacks of tremor in different muscles. 



Baglioni referred these fundamental differences to the different 

 point of attack of the two poisons upon the spinal cord. He 

 found that if carbolic acid were applied to the cells in the dorsal 

 or posterior part of the cord, while the ventral cells were spared, 

 clonic contractions of the limbs appeared ; but if strychnine was 

 subsequently applied to the same region, it failed to elicit tetanic 

 action. These and other experiments led Baglioni to conclude 

 that the action of strychnine is confined to the cells of the dorsal 

 part of the cord (sensory or co-ordinating ganglion cells of the 

 dorsal horn), while phenol has a selective action upon the cells of 

 the ventral part of the cord (motor ganglion cells of the ventral 

 horn). 



In subsequent researches upon other animals Baglioni (1904-9) 

 confirmed and amplified the theory of the elective action of 

 strychnine and phenol upon specific central cells, and claimed 

 that it is a physiological method by which the existence of sensory 

 central elements reacting to strychnine and of motor elements 

 reacting to phenol can be readily detected. He also found that the 

 central nervous system of invertebrates contains elements that react 

 to one or the other of these two poisons. In Cephalopoda the 

 ganglion stellatum of the mantle consists of ganglion cells, which 

 react exclusively to the action of phenol and cause clonic spasms 

 in the muscles innervated by them, while they are entirely unaffected 

 by strychnine, which, on the other hand, attacks the higher central 

 ganglia of the head, "and produces tetanic convulsions similar to 

 those seen in vertebrates. Fr. W. Frohlich (1910) confirmed and 

 amplified Baglioni's work on Cephalopoda. 



In the higher vertebrates also (dogs), strychnine and carbolic 

 acid exhibit an elective exciting action on the different ganglion 

 cells. Baglioni and Magnini (1909) noticed the remarkable fact 

 that strychnine, besides picking out cells in the dorsal region of 

 the cord and bulb, will also attack the ganglion cells of the 

 excitable zone of the cerebral cortex, and excite them to activity. 



