VIII.] 



SALIVARY DIGESTION. 



67 



Since, however, this amount of haemoglobin was obtained from 20. 1 86 grains 

 of the original blood, the amount in 100 parts will be found as follows : 



20.186 : 100 : : 2.784 : x 

 x = 1 3- 79 grams per cent. 



12. Microspectroscopes. When very small quantities of fluid are to be 

 examined, they are placed in small vessels made by fixing short lengths of 

 barometer tubing to a glass slide. Use either the instrument of Browning or 

 that of Zeiss (figs. 39, 40). 



The instrument is in reality an eyepiece with a slit mechanism adjustable 

 between the field glass and eye glass of an ocular. The instrument is fitted 

 into the tube of a microscope in place of the eyepiece. It consists of a drum 

 (A) with a slit adjustable by means of the screws H and F (fig. 40). Within 

 the drum there is also a prism whereby light admitted at the side of the drum 

 is totally reflected towards the eye of the observer. Above tho eye-glass is 

 placed an Amici prism of great dispersion, which turns aside on the pivot (K) 

 to allow of the adjustment of the object. It is retained in position by the 

 catch (L). At N is placed the scale of wave-lengths, and its image can be 

 projected on the spectrum by the mirror (0). The scale is adjusted relative 

 to the spectrum by the screw P. The scale is set by the observer so that 

 Fraunhofer's line D corresponds to 58.9 of the scale. 



The fluid to be examined is placed in a suitable vessel on the stage of the 

 microscope, and light is transmitted through it. 



LESSON VIII. 



SALIVARY DIGESTION. 



1. To Obtain Mixed Saliva. Rinse out the mouth with water 

 an hour or two after a meal. Inhale the vapour of ether, glacial 

 acetic acid, or even cold air through the mouth, which causes a 

 reflex secretion of saliva. In 

 doing so, curve the tongue *\ 

 so as to place its tip behind " 

 the incisor teeth of the upper 

 jaw. Or chew a piece of : ' 

 caoutchouc. In a test-glass 

 collect the saliva with as few 

 air-bubbles as possible. If 

 it be turbid or contain much 

 froth, filter it through a small 



H 



filter (p. 60). FIG. 41. Microscopic Appearances of Saliva. 



2. I. Microscopic Examination. With a high power observe 

 the presence of (i) squamous epithelium, (2) salivary corpuscles, 



