Nutrition 127 



Further, calves lacking ruminant organisms do not require dietary niacin. 

 Niacin-deficient dogs and foxes"*^- ^'" develop "blacktongue," which is 

 cured by feeding nicotinic acid. In dogs a diet of 0.25 mg./kg./day prevents 

 "blacktongue" and permits weight gain; half that amount controls "black- 

 tongue" but does not permit weight increase. ^^ In man pellagra results in 

 part from a deficiency of nicotinic acid. There is much evidence that "black- 

 tongue" and pellagra are complex conditions, part of which result from niacin 

 deficiency and part from a diet rich in corn, a grain which is low in trypto- 

 phane. "'- 



Pyridoxine (Vitamin Bn, Pyridoxal, Pyridoxamine). Pyridoxine is a pyridine 

 derivative: 



CH.OH 



I 



A 



HOC C - CH.OH 



I " 



HaC - C C 



\ / 



N 



As pyridoxal phosphate, it is a prosthetic group in protein utilization, probably 

 as a co-transaminase, and it may also be concerned in fat metabolism. Pyridox- 

 ine is not a dietary requirement of flagellates, although its addition to the 

 medium stimulates the growth of Chilovionas. '""' It must be supplied in 

 relatively large amounts for optimal growth of Tetrahymena ''*' and Colpuda. 

 !■" Pyridoxine is a general requirement for insects except when synthesized 

 by symbiotic flora (1 able 24). Ruminant mammals obtain sufticicnt pyridox- 

 ine from their rumen bacteria, the rumen contents of sheep containing ten 

 times as much as the food, and milk containing similar amounts whether the 

 cows are on high or low pyridoxine diet."-'' Birds and nonruminant mammals 

 require pyridoxine in their diet. Pyridoxine-deficient ducklings show retarded 

 growth and anemia. Convulsions appear in extremely deficient rats and pigs, 

 dermatitis in rats, and anemia in dogs, foxes, and pigs. The existence of 

 pathological conditions from pyridoxine deficiency in man is not established, 

 and there is evidence for its synthesis by man. 



Pantothenic Acid. Pantothenic acid has the following structure: 



CHa OH 



1 I 

 HOCH. - C - CH - CONH - (CH,). - COOH 



jHa 



k 



Pantothenic acid acts as a coenzyme in acetylation processes, for example, in 

 acetylation of choline to form acetylcholine. It is needed for optimal growth of 

 Tetrahymena, "'' and Colpidiiim, -"■' but added pantothenate does not stim- 

 ulate the flagellate Chilomonas.'^^-' Pantothenic acid favors survival of the 

 malaria organism, Plasmodium lophurae, in vitro. '•'"' Several insects of 

 different groups have been shown to require pantothenic acid, even when 

 not depleted of microorganisms, and more severe consequences result from 



