106 



The particular characters of the gum amidine, and other products 

 of the fermentation of starch, are described at length in notes an- 

 nexed to this paper ; in one of which the author remarks, that the 

 fixation of the elements of water, in the treatment of animal and 

 vegetable substances by the common principles of the laboratory, 

 occurs more frequently than is generally believed ; and shows, by a 

 comparative analysis of hog's lard in its recent state and after sapo- 

 nification, that the new properties which oils and fats acquire by 

 saponification, is chiefly referable to the fixation of the elements of 

 water. 



On Corpora Lutea. By Sir Everard Home, Bart. V.P.R.S. Read 

 January 14, 1819. [Phil. Trans. 1819, p. 59.] 



In this paper the author describes the origin, growth, use, and de- 

 cay of the Corpora lutea. The ovarium, before puberty, is a loose, 

 open texture, in which are a number of globular cells. After pu- 

 berty, the Corpus luteum forms in the substance of the ovarium. In 

 the cow it appears, when magnified, as a mass of convolutions, some- 

 what like the brain. Sir Everard then proceeds to describe the draw- 

 ings which accompany this paper, and of which the object is to show 

 that the Corpora lutea are the structures in which the ova are formed ; 

 that they exist previous to, and perfectly independent of, sexual in- 

 tercourse ; and that, when they have fulfilled their office of forming 

 ova, they are destroyed by absorption, whether the ova are impreg- 

 nated or not. 



On examining the appearance of the Corpora lutea before and after 

 impregnation, it appears probable that impregnation is necessary for 

 the expulsion of the ovum ; but when impregnation does not take 

 place, the ovum appears to remain in the cavity of the Corpus luteum. 

 Hence it may be concluded, that impregnation takes place in the 

 ovarium itself. 



Remarks on the Probabilities of Error in Physical Observations, and 

 on the Density of the Earth, considered, especially with regard to 

 the Reduction of Experiments on the Pendulum. In a Letter to 

 Capt. Henry Kater, F.R.S. By Thomas Young, M.D. For. Sec. 

 R.S. Read January 21, 1819. [Phil. Trans. 1819, p. 70.] 



In the first section of this letter, Dr. Young proceeds to examine 

 in what manner the apparent constancy of many general results, sub- 

 ject to numerous causes of diversity, may be best explained ; and 

 shows that the combination of many independent causes of error, 

 each liable to incessant fluctuation, has a natural tendency, depen- 

 dent on their multiplicity and independence, to diminish the aggregate 

 variation of their joint effect ; a position illustrated by the simple case 

 of supposing an equal large number of black and Avhite balls to be 

 thrown into a box, and 100 of them to be drawn out at once or in 

 succession ; when it is demonstrated that there is 1 chance in 1 2 ; 



