On slight ailments : and on treating disease / by Lionel S. Beale.
- Lionel Smith Beale
- Date:
- MDCCCXC [1890]
Licence: Public Domain Mark
Credit: On slight ailments : and on treating disease / by Lionel S. Beale. Source: Wellcome Collection.
Provider: This material has been provided by King’s College London. The original may be consulted at King’s College London.
317/398 page 307
![as do tlie contiguous capillaries o( the skin continuous with them. Now you are probably aware that when we blush, the cutaneous capillaries ol the cheeks are suddenly distended, their diameter, of course, being con- siderably increased. If it were not so, the difference in the quantity of blood would not be sufficient to produce the intensity of colour which is so remarkable. You see, then, that an instrument which is much less than the smallest needle, having passed directly through the skin, cjuickly leads to dilatation of the capillary vessels for a certain distance, perhaps the one-si.\teenth of an inch or more, around the line of perforation; but none of the vessels beyond the circumscribed line are dilated, though these freely communicate with the dilated vessels. Does this action de])end upon some influence exerted upon certain fine nerve-fibres lying in the course of the wound, or is it due to any direct influence upon the vessels themselves ? This last suggestion may be dismissed at once, because by no direct influence upon vessels of which w^e have know- ledge can such a phenomenon be produced. There is no doubt whatever that the change in the diameter of the vessels is occasioned by injury to the nerves, and it is probable that the congestion of the capillaries depends, not upon direct injury done to nerves by the passage of the lancet of the flea, but upon the influence exerted on the nerves in con- sequence of the escape of a small quantity of irritating poisonous material, which is extruded at the same time, and poisons and irritates the nerves in the course of the wound and those at a short distance around the line of penetration. This disturbance necessarily occasions change in the nerve-centre. Alterations of Calibre of tlie Smali Arteries.—The redness of the flea-bite is due to dilatation of the capillaries, but w'hat is very remark- able and of great interest is this—that the little arteries which communi- cate with and supply the capillaries with blood are dilated to a certain definite extent. Of this you may convince yourselves by trying the fol- lowing little experiment. Press the finger firmly upon the skin corre spending to the flea-bite and skin around it, so as to drive the blood from the distended vessels into the neighbouring capillaries. The whole of the skin subjected to pressure of course becomes perfectly pale, the area corresponding to the flea-bite being as pale as the skin around, from the capillaries of w’hich the blood has been temporarily driven. Now' a few' seconds after the finger has been removed, the Iflood streams back into the vessels of the area of the skin rendered pale by the pressure, so as to restore the exact tint which existed before. The flea-bite ivill resume the precise degree of redness it had before pressure was applied, being neither paler nor darker. I'he pressure has caused only a temporary change. Although the blood had been completely squeezed out of the capillary vessels, the moment it is X 2](https://iiif.wellcomecollection.org/image/b2130340x_0317.jp2/full/800%2C/0/default.jpg)
