482 MANUAL OF HISTOLOGY. 



The development of the stomach is a subject in the history of develop- 

 ment to which great interest attaches. We will, however, occupy our- 

 selves only with its accessory organs. These, the tubular glands, commence 

 in the form of pointed processes, springing downwards from the intestinal 

 glandular germinal plate, which become gradually hollow, beginning at 

 the openings. It is a point worthy of notice, that these glands are for 

 a long time entirely unconnected with the subjacent loose fibrous intestinal 

 layer ; and it is not until the fifth month of intrauterine life that the 

 latter sends up tufted processes between the gastric tubuli to form the 

 mucosa of the part (Koelliker). 



253. 



The mucous membrane of the non-functioning stomach is pale in 

 colour, and more or less completely covered by a quantity of either 

 slightly acid or alkaline slimy mattter of considerable viscidity. This is 

 the secretion elaborated by the gastric mucous glands. In it may be seen, 

 under the microscope, beside cast-off columnar epithelium, numerous 

 peptic cells escaped from the peptic tubuli, and frequently, also, a 

 number of more or less broken down structures of the same nature, naked 

 cells, and free nuclei surrounded by particles of the original cell contents. 



According to Brucke and Bernard, it is only the surface of the mucosa 

 which is acid in the living animal, the deeper portions having an alkaline 

 reaction. After death the whole becomes rapidly acid owing to diffusion. 



On the introduction of food into the stomach, or under the influence 

 of other chemical or mechanical excitants of the gastric mucous mem- 

 brane, the condition of things is immediately changed. Owing, probably, 

 to some reflex action not yet understood, although indicated in many 

 ways, an increased influx of blood into the intricate vascular interlacements 

 of the mucosa takes place. The veins become distended, and contain 

 brighter blood, and the whole surface appears to the unaided eye of a more 

 or less rose-red colour, in addition to which phenomena the temperature 

 rises. Coincident with these changes the gastric juice commences to 

 well up from the tubules, bearing with it numerous peptic cells from the 

 lining of the latter. 



This juice is a transparent fluid of strongly acid reaction, either perfectly 

 colourless or of a pale straw tint. It takes up certain constituents of the 

 mucous coating of the stomach, and extracts subsequently various fer- 

 menting substances from the granular contents of the peptic cells, a 

 process which commences while the juice is still within the tubuli in 

 which the peptic cells are contained. It is likewise mixed with 

 whatever saliva may have been swallowed. It cannot then be a matter 

 of surprise that the gastric juice possesses a specific gravity of I'OOl, 

 1-005, and 1-010. 



The proportion of solid constituents in this secretion is, as a rule, 

 small but variable. Thus, in the sheep, it contains, according to Bidder 

 and Schmidt, 1'385, and in the dog, 2'690 per cent., while, according to 

 the last named observer, that of the human female only contains 0-559 

 per cent. The nature of the fluid also would lead us to expect consider- 

 able variety also in one and the same individual. 



The two most important of these constituents are a free acid and 

 peculiar fermenting substance, which possesses in the presence of the 

 former, and only then, a great amount of energy. 



The add in question has given rise to much debate regarding its 



