222 CHANGES IN THE CAPILLARIES. [BOOK i. 



capillaries. In the normal circulation only a few white corpuscles 

 are from time to time seen in this situation slowly moving on 

 in jerks ; but now the walls of the veins seem to be more and 

 more thickly lined with white corpuscles, which are at first com- 

 pletely stationary. At the same time white corpuscles become 

 also very abundant in the capillaries. Very soon these white 

 corpuscles may be seen, either through stomata at the junctions of 

 the epithelioid cells forming the lining of the vessels, or by 

 temporary breaches which are rapidly repaired, making their way 

 through the walls of the veins and capillaries, and escaping into 

 the surrounding tissues. Through the walls of the capillaries and 

 smaller veinlets, red corpuscles pass as well as white. And this 

 takes place to such an extent that very soon the tissue around the 

 veins and capillaries becomes crowded with white corpuscles, and to 

 a less extent with red corpuscles which have made their way out 

 of the vessels. At the same time a large quantity of coagulable 

 lymph, which since it appears also to have passed from the blood- 

 stream through the walls of the blood-vessels is spoken of as exu- 

 dation, makes its appearance in the interstices of the inflamed 

 tissue. While however these changes are going on there is not, as 

 in stasis, a delay and final arrest of the blood-stream. On the 

 contrary, the flow through the widened channels continues during 

 the whole time to remain accelerated. By comparing the outflow 

 from the veins of the inflamed foot of a dog, with the outflow from 

 the veins of the healthy foot, it has been ascertained that a larger 

 (quantity of blood passes through the inflamed foot than through 

 the healthy foot in the same time. 



We must not however pursue this subject of inflammation any 

 further. We have simply brought it forward as affording another 

 illustration of the action of the walls of the blood-vessels; for, 

 though the matter is perhaps not definitely settled, it seems pro- 

 bable that the aggregation, in inflammation, of the white corpuscles 

 upon the lining surface of the vessels is due to a special attraction 

 which the blood-vessels exert on the white corpuscles, without pro- 

 ducing that general adhesion of all the corpuscles which is the mark 

 of stasis, and that the migration of the corpuscles is also at least 

 facilitated by similar intrinsic changes in the vascular walls. 



We cannot say at present whether the vascular walls are also 

 capable of modifying the passage of the fluid parts as distinguished 

 from the corpuscular elements of the blood, though we know by 

 experiment that the flow of fluid through capillary tubes may be 

 modified on the one hand by changes in the substance of which the 

 tubes are composed, and on the other hand by changes in the 

 chemical nature (even independent of the specific gravity) of the 

 iluid which is used. We have said enough to shew that the peri- 

 pheral resistance in the capillaries (and consequently all that depends 

 on that peripheral resistance) is not merely a matter of the mechani- 

 cal friction of the blood against the smooth walls of the blood-vessels, 



