2 PRACTICAL HISTOLOGY. 



glass). Place a small piece of blotting-paper on the slide at the edge of the cover-glass opposite 

 to the spot where the drop of acid was placed, which will have the effect of drawing the acid 

 under the cover so as to ' irrigate ' the blood-corpuscles with the reagent. Steadily observe 

 one or two corpuscles ; they will gradually enlarge, become globular and all of a sudden swell 

 up and become distinctly spherical, and then as suddenly collapse and ' shoot ' or discharge their 

 haemoglobin. The nucleus comes clearly into view during the process. This process ought to 

 be diligently looked for, because the phenomenon is so striking. It is as if the corpuscle burst 

 and discharged something. After the collapse, the residue of the stroma adheres to the nucleus. 

 In other cases the corpuscles do not collapse, but remain globular, clear, and transparent. The 

 peri-nuclear part becomes decolourised, and appears to be limited externally by a membrane 

 from which fine shreds the residue of the stroma stretch to the nucleus, which is now clearly 

 brought into view, and has assumed a distinctly granular appearance, due to the existence of 

 a fibrillar network in its interior. If the acid used be too strong this action may be missed, 

 and the outline of the corpuscles becomes very faint, and the shrivelled nucleus may appear 

 cxcentrically, or may even escape altogether outr-ide the corpuscle. These phenomena are 

 best observed with frog's blood. 



(b~) Acetic Acid. Shows the same phenomena, though in a less degree. The corpuscles 

 swell up and become clear, so that their nucleus becomes very obvious, and the nucleus not 

 unfrequently passes out of the corpuscles. It is to be noted that all the corpuscles are not so 

 affected, which is perhaps due to difference in the chemical constitution of the corpuscles. In 

 many corpuscles distinct vacuoles are formed in the peri-nuclear part. The coloured pig- 

 ment may be seen gradually to leave the wall of the corpuscle, and become heaped up round 

 the nucleus. The fluid in which the corpuscles float becomes slightly coloured by a diffusion 

 of the pigment of the blood-corpuscle (haemoglobin), and sometimes the nucleus takes up 

 some of this pigment and becomes of a distinctly yellow colour (PI. I., Fig. 3). 



(c) Water. Squeeze out another drop of blood on to a slide, cover, and irrigate with water 

 in the manner just described. The corpuscles and their nuclei both swell up and become 

 globular, owing to endosmosis, and at the same time the haemoglobin diffuses into the sur- 

 rounding fluid (PI. I., Fig. 6). 



(cf) Syrup. Squeeze out a fresh drop of blood, add a drop of strong syrup of white cane 

 sugar, and mix the two drops thoroughly with the point of a needle, and apply a cover-glass. 

 Owing to the greater specific gravity of the syrup the corpuscles lose fluid, and, on examina- 

 tion some of them present a shrivelled appearance, and resemble thin misshapen biscuits, 

 while others are but slightly affected. Here and there a reddish tinge is seen in a corpuscle 

 (PI. I., Fig. 4). 



(i) Dilute Alcohol. One part of rectified spirit to two of water, applied in the same way 

 as acetic acid, decolourises the corpuscles, causes them to swell, and brings a nucleolus into 

 view (usually placed towards one end) in each nucleus (Ranvier, Stirling). 



(/) Magenta. Mix a drop of blood with a drop of a solution of sulphate or nitrate of 

 rosaniline (p. xliv), cover and examine. The nuclei of the coloured corpuscles become stained 

 of a deep red colour, the peri-nuclear part remaining unaffected, though of course the magenta 

 has to traverse it to reach the nucleus. All the corpuscles are not, however, equally affected. 

 In many the indications of the existence of an envelope with one or more thickenings in it 

 are observable. This last appearance is even better seen if the magenta be added after the 

 blood has been irrigated with dilute alcohol. 



() Tannic Acid. Mix a drop of the blood with a drop of a freshly prepared two per cent, 

 aqueous solution of tannic acid (made with hot water and allowed to cool) ; cover and 



