Stepp was led by the experiments of Fingerling (2) to investigate the problem whether birds differ from mammals in their capacity to synthesize the complex lipins. It was shown by Fingerling, and simultaneously and independently by McCollum, Drescher and Halpin (3) that birds may be satisfactorily nourished on diets very poor in lipins of every kind. McCollum, Drescher and Halpin fed three half-grown hens exclusively on a mixture of polished rice and skim milk powder, the latter having been extracted with ether to render it essentially free from fats. On this diet the hens increased their body weights about 33 per cent, and laid 57 eggs. These eggs collectively contained 82.95 grams of lecithin and cephalin. This is several times the amount of these substances contained in the entire tissues of the hens.

Fingerling fed his ducks on a diet consisting of 300 grams cooked potatoes, 80 grams cooked blood albumin, 300 grams of boiled starch, 10 grams of calcium phosphate and 10 grams of calcium carbonate per bird per day. The ducks had completed their growth before the beginning of the experiment. One duck was estimated to have deposited in her eggs 302.3 grams of lecithin, another 246.0 grams and another 212.7 grams. The birds remained in good health during the egg-laying period. This diet would not have maintained them through a second laying period.

Stepp (4) sought to determine whether pigeons differ in their nutritive requirements from mammals. He fed three pigeons exclusively on dog biscuit which had been very completely extracted with hot alcohol. All were dead at the end of 43 days. The cause of death was polyneuritis, the analogue of beri-beri in man. Another pigeon restricted to the same food was unable to stand on the 38th day because of weakness and polyneuritis. It was then given doses of a commercial "vitamin" preparation (oryphan) plus an alcoholic extract of egg yolk to furnish the lipins which Stepp believed to be indispensable for mammals. The bird rapidly recovered and remained in good condition on this diet until the 92nd day of the experiment. It was then fed unextracted dog biscuit until the 98th day. The diet was then changed to extracted dog biscuit supplemented with the commercial preparation of the anti-neuritic substance (oryphan) but without the lipin extract. The body weight of the bird at this time was 271 grams. It had been observed on the experimental diets for 117 days. On this lipin-free diet it steadily, but slowly, lost weight so that by the 193rd day it weighed but 217 grams. It still ate well, but its flight was unsteady. Unextracted dog biscuit was fed for two days. The pigeon was then given the extracted dog biscuit without the addition of either lipins or "vitamin." The result was a rapid loss in weight, and the development of symptoms of polyneuritis. Death occurred on the 233rd day.

From these observations Stepp drew the unwarranted conclusion that the bird does not require the indispensable lipins or substance which accompanies them, which he had demonstrated to be necessary in the nutrition of mice. The steady loss of weight of his pigeon when the lipin extract was omitted from the diet shows clearly that its nutrition during this part of the experiment was not satisfactory. These results do not warrant Stepp's conclusion that there is a difference in the nutritive requirements of birds and mammals.