274 NUMERICAL LAW OF REGRESSION 



Results. 



In the following paragraphs we shall indicate in each case: (1) 

 information relating to the bird under observation; (2) a graphic 

 chart on which are shown the observed curve and the parabola which 

 most nearly approximates it; the latter departs from the horizontal 

 at the point where regression begins and becomes tangent to the hori- 

 zontal at the point where regression ends. This parabola may be 

 represented algebraically by the formula 



in which L represents the length of the comb at a given time during 

 regression, I the length of the comb at the end of regression, C an indi- 

 vidual constant, 9 the total period of regression, and t the time corre- 

 sponding to the unknown ordinate L. 



Experiment 1. — Cock, Dorking, about 1 year old. Sex characters well devel- 

 oped; combs and barbules scarlet; sexual instincts well developed. 



Castrated Mar. 20, 1912. Both testicles very large, total weight 42 gm. 

 Regression of the comb began at once and was finished at the end of 12 

 weeks (Fig. 3). There was coincidence between the observed curve and the 

 parabola throughout almost the entire length of the curve: only at Point 6 of the 

 ordinate was there a deviation, regression having been accelerated by a cause 

 unknown to us; after that the acceleration was compensated for, since the phe- 

 nomenon resumed its normal curve. 



Experiment 2. — Cock, Beauceronne, about 6 months old. Secondary sex char- 

 acters in course of development but not completely developed. Comb brilliant 

 but not yet of its final length. Completely castrated Jan. 18, 1912. Regression 

 began immediately and continued for 7 weeks (Fig. 4.) There was the best 

 possible coincidence throughout the entire extent of the curve. 



The weight curve (shown by the broken line, the scale of weight 

 being found at the right) indicates clearly that the curves are inde- 

 pendent of each other and that the phenomenon of regression fol- 

 lows its regular course irrespective of the general nutrition of the 

 bird. Regnault and then Pfliiger later have shown that the body 

 regulates its consumption not according to the substances which are 

 offered it but according to the demands of the cells. Here we see 

 clearly that the needs of the cells are in their turn influenced by the 

 testicles, and that their nutrition is independent of the general 

 metaboUsm. 



