346 HISTORICAL. 



(drosera) possesses, upon the surface of its leaves, numerous tentacle-like processes, 

 provided with glands. As soon as an insect lights upon the leaf, the former is 

 suddenly seized by the tentacles. The glands discharge a juice of acid reaction 

 and digest the animal with the exception of its insoluble chitinous remains. The 

 juice contains a pepsin-like ferment and formic acid. The secretion, as well as, 

 later, the absorption of the dissolved substances, takes place in conjunction 

 with movement of the protoplasm of the leaf-cells. Venus' fly-trap (dionea) and 

 butter-wort (pinguicula) exhibit similar processes, as well as the cavities of the 

 transformed leaves of the nepenthe. Altogether, about 15 species of .such 

 carnivorous dichotyles are known. 



The juice escaping from incisions in the green fruit of the papaw-tree (carica 

 papaya) possesses peptonizing properties due to a ferment closely allied to trypsin. 

 The milky sap from the fig-tree is likewise active, exerting a diastatic effect and 

 also coagulating milk at 50 C. Albumin is dissolved also by some fungi (boletus, 

 tuber) , lichens (parmelia) and the sap of taraxacum, lactuca, agave and portulac. 

 Artichokes, yellow or lady's bedstraw and other plants contain rennet-ferment. 

 The sap of aloes and of sugar-cane, as well as dried figs, coagulates milk and has 

 a peptonizing action; as does also ordinary flour-dough on admixture; further, the 

 juice (containing peptone at the same time) from the seed of wheat, barley, 

 poppy, beets and corn, after the addition of organic acids. Potatoes and rice 

 have feeble, flour, grain and corn marked sugar-forming activity. 



HISTORICAL. 



Digestion in the Mouth. The vessels of the teeth were known to the Hippo- 

 cratic school. Aristotle ascribed an uninterrupted growth to the teeth. In 

 addition, he directed attention to the fact that those animals that exhibit a devel- 

 opment of horns and antlers, cloven-hoofed animals, possess an imperfect denture 

 (absence of the upper incisor teeth) . It is a remarkable fact that, in human beings 

 with excessive formation of horny substance, in consequence of the presence 

 of superfluous hair, imperfect development of the teeth (absence of the incisors) 

 has also been observed. The muscles of mastication were recognized early. 

 Vidius (died 1567) described the maxillary articulation, with the meniscus. The 

 epiglottis, according to Hippocrates, prevents the entrance of food into the 

 larynx. The ancients considered the saliva only a solvent and a means for 

 moistening the food. In addition, in consequence of a knowledge of the saliva of 

 rabid animals and the parotid secretion of venomous snakes, various poisonous 

 properties were ascribed to the saliva, especially from fasting animals a view 

 that Pasteur again confirmed in part, referring the action to pathogenic bac- 

 teria in the secretions of the mouth. Aretasus (81 A. D.) emphasizes the 

 muscular nature of the tongue. The salivary glands had been discovered in 

 ancient times. Galen (131-203 A. D.) was familiar with Wharton's duct and 

 ^tius (270 A. D.) with the submaxillary and sublingual glands. Regner de Graaf 

 established salivary fistulas in dogs in 1663, by tying tubes in Stenon's duct. 

 Hapel de la Chenaye obtained in 1780 for examination large amounts of saliva 

 from a salivary fistula established in a horse. Spallanzani in 1786 stated that 

 insalivated articles of food are more readily digested than those moistened with 

 water. Hamburger and Siebold investigated the reaction, consistency and 

 specific gravity of the saliva and found mucus, proteid and salts present. Ber- 

 zelius introduced the term ptyalin for the characteristic substance in the saliva, 

 though Leuchs in 1831 first discovered its diastatic fermentative action. 



Gastric Digestion. The ancients compared digestion to cooking, through which 

 solution is effected. Aristotle supposed that, through this "pepsis" chyle 

 (ichor) first developed from the food, and then reached the heart. He also 

 knew of the rennet-action of the stomach. According to Galen, only dissolved 

 masses pass through the pylorus into the intestine. He described the 

 movement of the stomach and the peristalsis of the intestines. ^Elian recognized 

 the four stomachs of ruminants and gave their names. Vidius (died 1567) 

 observed the numerous small glandular openings in the gastric mucous mem- 

 brane, van Helmont (died 1644) expressly mentions the acid of the stomach. 

 He as well as Sylvius (died 1672) compared the action of the stomach with 

 fermentation, in connection with which, according to Descartes (died 1650) and 

 Willis (died 1675), the action of the acid predominates. Reaumur (1752) 

 recognized that a juice was secreted by the stomach that effects solution and 

 with which, together with Spallanzani (1777), he undertook digestive experi- 



