October 23, 190S] 



SCIENCE 



571 



excluded by various chemical and physio- 

 logical tests. Search was also made for a 

 radio-active substance. Chemists had called 

 attention to the abundance of calcium in the 

 ash; this and strontium were excluded from 

 being the toxic agents. 



Finally Crawford noticed that extracts pre- 

 pared with sulphuric acid were inactive; 

 further, that active extracts caused a rise of 

 blood-pressure. Both of these observations 

 suggested the presence of barium. After a 

 long series of careful experiments the author 

 reached the following conclusions : 



A close analogy exists between the clinical 

 symptoms and pathological findings in barium 

 poisoning and those resulting from feeding ex- 

 tracts of certain loco plants. Small doses of 

 barium salts may be administered to rabbits with- 

 out apparent effect, but suddenly acute symptoms 

 set in analogous to what is reported on the range. 



Finally barium was found in the ash of 

 many " loco " plants in amounts sufficient to 

 account for the symptoms. 



Among the other important conclusions, 

 some of which help to explain the unsatis- 

 factory results of former workers, are the 

 following : 



Loco plants grown on certain soils are in- 

 active pharmacologically and contain no barium. 

 In drying certain loco plants the bariimi appar- 

 ently is rendered insoluble so that it is not ex- 

 tracted by water, but can usually be extracted by 

 digestion with the digestive ferments. 



The barium to be harmful must be in such a 

 form as to be dissolved out by digestion. 



In deciding whether plants are poisonous it 

 is desirable not merely to test the aqueous or 

 alcoholic extract, but also the extracts obtained 

 by digesting these plants with the ferments which 

 occur in the gastro-intestinal tract. 



These experiments afford another illustra- 

 tion of how indispensable are animal experi- 

 ments in all kinds of pharmacological work. 



The author conservatively limits his conclu- 

 sions to the plants he has studied, and recog- 

 nized that in the plants grown in other locali- 

 ties the toxic action may be due to substances 

 other than barium. 



There is an extraordinarily rich and well- 

 selected bibliography of the entire subject of 



" loco " and also of barium poisoning in both 

 man and the domestic animals. 



It seldom falls to the lot of an investigator 

 to carry to such a successful conclusion a 

 problem of such complexity and so baffling; 

 it will long remain as one of the most notable 

 contributions to pharmacology made here or 

 abroad. Eeid Hunt 



Hygienic Laboratory, 

 Washington, D. C. 



SPECIAL ARTICLES 



THE EFFECT OP LESIONS OF THE DORSAL NEm'E 



ROOTS ON THE REFLEX EXCITABILITY OP 



THE spinal cord (PRELIMINARY 



note)' 



In some preliminary experiments Professor 

 Carlson found that lesions of the dorsal nerve 

 roots appear to have the same effect on the 

 cross reflexes of the spinal cord as transsection 

 of the cord itself. That is, in animals in 

 which the reflexes disappear temporarily after 

 transsection of the cord (spinal shock) the 

 cross reflexes are similarly lost temporarily 

 after lesions of the doreal nerve roots on one 

 side. 



The experiments here reported were under- 

 taken at the suggestion of Professor Carlson 

 in order to determine definitely this parallel- 

 ism in different animals, because of the im- 

 portant bearing of these results on the theories 

 of spinal shock. 



Methods of Experiments. — Section of the 

 dorsal nerve roots to one limb : (a) After high 

 section of the spinal cord, (b) on the intact 

 animal. 



In pigeons, cats and dog's after the high 

 section and recovery from shock and an- 

 assthesia (usually one day) the final operation 

 of cutting the dorsal nerve roots was made 

 without anaesthesia. 



BesuUs of Experiments. — The effect on the 

 cross reflexes caused by the cutting of the 

 dorsal roots to a limb is as follows : In snap- 

 ping turtles, loss of cross reflexes for 5-10 

 minutes; in frogs, loss of cross reflexes for 

 15-30 minutes ; in pigeons, no loss of reflexes ; 



^ From the Hull Laboratory of Physiology, Uni- 

 versity of Chicago. 



