70 THE PRINCIPLE OF THE DIRECT CHAP. III. cries or groans. Almost every muscle of the body is brought into strong action. With man the mouth may be closely compressed, or more commonly the lips are retracted; with the teeth clenched or ground together. There is said to be " gnashing of teeth " in hell; and I have plainly heard the grinding of the molar teeth of a cow which was suffering acutely from inflammation of the bowels. The female hippopotamus in the Zoo- logical Gardens., when she produced her young., suf- fered greatly; she incessantly walked about., or rolled on her sides, opening and closing her jaws, and clatter- ing her teeth together.4 With man the eyes stare wildly as in horrified astonishment, or the brows are heavily contracted. Perspiration bathes the body, and drops trickle down the face. The circulation and respiration are much affected. Hence the nostrils are generally dilated and often quiver; or the breath may be held . until the blood stagnates in the purple face. If the agony be severe and prolonged, these signs all change; utter prostration follows, with fainting or convulsions.. A sensitive nerve when irritated transmits some in- fluence to the nerve-cell, whence it proceeds; and this transmits its influence, first to the corresponding nerve- cell on the opposite side of the body, and then upwards and downwards along the cerebro-spinal column to other nerve-cells, to a greater or less extent, according to the strength of the excitement; so that, ultimately, the whole nervous system may be affected.5 This involuntary trans- mission of nerve-force may or may* not be accompa- 4 Mr. Bartlett, " Notes on the Birth, of a Hippopota- mus," Proc. Zoolog-. Soc. 1871, p. 255. 5 See, on this subject, Claude Bernard, * Tissus Vivants,' 1866, pp. 316, 337, 358. Virchow expresses himself to al- most exactly the same effect in his essay " Ueber das Rtickenmark" (Sammlung- wissenschaft. Vortrage, 1871, s. 28).