104 THE VITAMINS 



The question has occasionally been raised as to whether or not the 

 rat is a suitable animal for use in studies of the antineuritic vitamin. 

 The symptoms of the specific deficiency (polyneuritis) had not in the 

 past been produced with regularity in rats, and because of this, doubt 

 has arisen as to the value of the rat growth technique. As recently as 

 1928 Kinnersley, Peters and Reader make the statement that "it is 

 not yet absolutely certain that rat tests can differentiate the curative 

 factor in the vitamin B complex." Chick and Roscoe (1927) rarely 

 observed symptoms of polyneuritis in their animals on their basal diet 

 K alone. 



Drummond (1917) noted paral)^ic symptoms in three only out of 

 a large number of rats on diets deprived of water-soluble vitamins. 

 Opposed to these negative results, Schaumann (1911) found that rats 

 confined to a diet of denatured horse flesh developed symptoms of 

 paralysis. He states that three rats on this diet became lame after 25 

 to 28 days on this diet. All three animals survived in this condition 

 for the eighty days of the experimental period. McCollum and Sim- 

 monds (1918) had observed paralysis in their rats as a sign of 

 depletion of the bodily store of vitamin B. Hofmeister (1922) was 

 able to produce symptoms of polyneuritis in rats with considerable 

 regularity. 



When the diet is lacking or is very low in vitamin B, rats may die 

 before the classical nervous symptoms of polyneuritis appear; whereas 

 a small amount of vitamin B will allow them to live longer, though 

 they may exhibit severe nerve symptoms for as long as three weeks 

 to a month. 



Beyond a certain minimum which does not prolong life sufficiently 

 to permit the development of polyneuritis, gradually increasing the 

 allowance of vitamin B first permits the full development of the disease, 

 while further increasing the allowance postpones the time of onset 

 and reduces the proportion of animals afflicted with observable symp- 

 toms. Head retraction is usually one of the earliest symptoms. In its 

 mildest form it appears as a nervous jerking of the head when the 

 animal becomes excited. Animals are apt to hold their heads on one 

 side and walk in circles. In more aggravated cases the opisthotonic 

 position of the head is quite marked. There is sometimes complete 

 paralysis of the hind legs, but more frequently the nervous involvement 

 manifests itself in a spastic gait, or in loss of muscular control, espe- 

 cially when handled. In many cases this loss of control results in ani- 

 mals becoming prostrated, sometimes rolling over completely many times 

 when attempting to move forward, and is probably comparable to 



