these glands have indicated that the large thyroids 

 from these moribund rats were reflecting, in part 

 at least, enlarged parathyroid glands. More de- 

 tails (54) are reported in a separate communication 

 dealing with the thyroid and parathyroid glands 

 from these rats as seen from microscopic examina- 

 tion. 



Rats fed SPM, SPB, and SPPB diets.— The 

 thyroid weights of rats fed SPM, SPB, and 

 SPPB diets are summarized in table 4S. Thyroids 

 similar in size to those found in rats fed stock or 

 SP S HVO diets were obtained from rats main- 

 taining weight on SPM diet; those from rats 300 

 to 600 days of age fed SPB or SPPB diets tended 

 to be somewhat larger. Enlarged thyroids were 

 seen freemen tly with SPPB diet, even in rats less 

 than 500 days of age regardless of weight loss. 

 Thyroids exceeding 20 mg. in weight were found 

 occasionally in animals that had lost more than 

 100 grams on each of the three diets, as well as 

 in older rats with weight loss less than 100 grams. 

 The thyroids from rats with a relatively long life 



span on SPM diet tended to be small in spite of 

 the large weight loss before sacrifice. 



Rats fed other experimental diets. — In 

 table 49 are summarized data for the thyroid 

 weights of rats fed the remaining experimental 

 diets; the results are for rats that were losing 

 weight, with the few exceptions indicated in 

 this table. Interpretation of the results in terms 

 of dietary response is complicated by variation in 

 weight loss in the different experimental series. 

 Data on rats maintaining weight or with weight 

 loss limited before sacrifice might reveal differ- 

 ences due to diet that are not apparent from the 

 data available. 



Thyroids were consistently large, regardless of 

 weight loss, for rats fed the various SPE supple- 

 mented diets, and were similar in size to thyroids 

 obtained from rats fed the unsupplemented SPE 

 diet. The kind of fat (HVO, lard, or butter) or 

 the level of fat (8 or 16 percent) appeared to be 

 without influence on the size of this gland. Re- 

 placement of egg white for casein in the semipuri- 



Table 48. — Thyroid weights for rats maintaining or losing weight at different ages on SPM, SPB, and 



SPPB diets^ 







Average 



Average 



Average 



Thyr 



Did weights 



Thyroids weighing- 





Weight status, diet, and 















age of rats (days) 



Rats 



age 



body 



weight 







Less 



10.0 to 



15.0 to 



20.0 









weight 



loss 



Average 



Range 



than 

 10.0 

 mg. 



14.9 

 mg. 



19.9 



mg. 



mg. 

 and 

 over 



Rats maintaining weight: 























SPM: 



Number 



Darjs 



Grams 



Grams 



Mg. 



Mg. 



Percent 



Percent 



Percent 



Percent 



Less than 300 .. 



13 



214 



553 







10. 5 



4. 3-14. 7 



46 



54 











300 to 499 



6 



399 



672 







11. 2 



4. 2-16. 7 



33 



50 



17 







500 to 599 



2 



550 



624 







11. 6 



7. 8, 15. 5 



50 



50 











SPB: 























Less than 300 _- 



13 



214 



520 







11. 5 



S. 1-15. 1 



38 



54 



S 







300 to 499 



7 



413 



596 







13. 1 



7. 0-27. 1 



29 



57 







14 



500 to 599 



3 



549 



673 







16. 1 



14. 1-17. 5 







33 



67 







SPPB: 























Less than 300. _ 



14 



217 



535 







12.5 



S. 2-19. 



21 



57 



21 







300 to 499 



5 



412 



644 







16. 



13. 3-19. 8 







60 



40 







500 to 599 



6 



550 



728 







15. 8 



9. 6-22. 



17 



33 



17 



33 



Rats losing less than 100 























grams: 























SPM: 























Less than 500 _. 



11 



358 



591 



49 



13. 6 



8. 4-1 S. 2 



IS 



45 



36 







500 and over 



6 



599 



74S 



44 



19. 1 



11. 9-34. 7 







50 



17 



33 



SPB: 























Less than 500. _ 



9 



308 



508 



46 



12. 8 



6. 2-19. 9 



33 



33 



33 







500 and over 



7 



671 



628 



53 



15. 



5. 7-23. 8 



14 



29 



43 



14 



SPPB: 























Less than 500 -- 



22 



338 



576 



42 



17. 2 



6. 2-27. 6 



5 



32 



32 



32 



500 and over 



10 



625 



618 



66 



16. 4 



12. 2-20. 5 







40 



40 



20 



Rats losing more than 























100 grams: 























SPM: 























Less than 500 . . 



6 



421 



532 



144 



22.2 



7. 1-46. 5 



17 



17 



17 



50 



500 and over 



8 



776 



563 



198 



15.7 



4. 6-30. 1 



12 



3S 



25 



25 



SPB: 























Less than 500- - 



5 



450 



469 



186 



22. 1 



12. 3-28. 4 







20 



20 



60 



500 and over 



13 



616 



505 



186 



23. 1 



10. 8-39. 







S 



31 



62 



SPPB: 























Less than 500 _. 



5 



397 



550 



192 



18. 8 



9. 5-29. 



20 



20 



20 



40 



500 and over 



7 



570 



522 



177 



24. ( 



13. 3-36. 5 







14 



14 



71 



60 



