590 DIGESTION. 



cuticular, of the massy glandular part, and of the portion near the pylo- 

 rus of the boar's stomach, being prepared as rennet, it was found, that 

 no part had the effect of producing coagulation but that near the pylorus, 

 where the gastric glands of the animal are especially conspicuous. The 

 crop and gizzard of a cock were salted, dried, and afterwards steeped in 

 water. The solution, thus obtained, was added to milk: the portion of 

 the crop coagulated it in two hours ; that of the gizzard in half an hour. 

 The contents of a shark's stomach and duodenum coagulated it instan- 

 taneously. Pieces of the stomach were washed clean, and steeped in 

 water for sixteen hours. The solution coagulated milk immediately. 

 Pieces of the duodenum produced the same effect. When the milk was 

 heated to 96, the coagulation took place in half an hour; when cold, 

 in an hour and a quarter. The stomachs of the salmon and thornback, 

 made into rennet, coagulated milk in four or five hours. 



But those experiments of Mr. Hunter do not inform us of the par- 

 ticular secretions that are productive of the effect. They would, indeed, 

 rather seem to show, that it is a general property of the whole internal 

 membrane. To discover the exact seat of the secretion, and especially 

 whether it be not in the gastric glands, Sir Everard Home 1 selected 

 those of the turkey ; which, from their size, are better adapted for such 

 an experiment than those of any other bird, except the ostrich. A young 

 turkey was kept a day without food, and then killed. The gastric glands 

 were carefully dissected separately from the lining of the cardiac cavity; 

 cutting off the duct of each before it pierced the membrane, so that no 

 part but the glands themselves were removed. Forty grains, by weight, 

 of these glands were added to two ounces of new milk; and similar ex- 

 periments were made with rennet; with the lining of the cardiac cavity 

 of the turkey; and with the inner membrane of the fourth cavity of 

 the calf's stomach. Coagulation and separation into curds and whey 

 were first effected by the rennet. Next to this, and simultaneously, 

 came the gastric glands, and the fresh stomach of the calf; and lastly, 

 the cardiac membrane of the turkey. From these experiments, Sir 

 Everard concluded, that the power of coagulation is in the secretion of 

 the gastric glands ; and that the power is communicated to other parts, 

 by their becoming more or less impregnated with it. 



The marginal figure, copied from an engraving of the microscopic 

 observations of Mr. Bauer, exhibits the gastric glands of the human 

 oesophagus magnified fifteen times. These glands are the lining of the 

 lower part of the oesophagus ; and have the appearance of infundibular 

 cells, whose depth does not exceed the thickness of the membrane. 

 This structure, although different from that of the gastric glands of 

 birds, is a nearer approach to it than is to be met with in any part of 

 the inner surface of the stomach or duodenum. It also resembles them, 

 in the secretion which it produces coagulating milk, whilst none of the 

 inspissated juices, met with in these cavities, according to Sir Everard, 

 affect milk in the same way. From these facts, he thinks, there can 

 be no longer any doubt entertained, that the gastric glands have the 

 same situation respecting the cavity of the stomach as in birds. Yet 



1 Lectures on Comparative Anatomy, i. 299, Loud., 1814, and iii. 134, Lond., 1823. 



