Chloroform is an irritant to the skin and mucous membranes. A drop left on the skin and covered over with impermeable material will produce a deep and painful blister. A drop falling into the eye, if not instantly washed away, produces a very powerful inflammatory reaction, and many eyes have been totally lost from carelessness in this respect. Such incidents are of course actionable, and heavy damages may be given. [Illustration: FIG. 35.--Diagrammatic representation of various blood pressure curves obtainable with chloroform. Line ABA′ represents curve desired in normal chloroform administration. Line ABCB′ represents gradual overdosage. Line ABCC′ represents recovery by inversion. DD′ represents syncope from vagal inhibition: in its course, one attempt of the heart to “escape” is shown.] The special peculiarities of the action of chloroform upon the nervous system have already been emphasised in the account given of the physiology of ether (see page 75). Its action upon the _circulatory and respiratory systems_ has been the subject of many researches, and of much embittered controversy. The literature is therefore very extensive, and the account of it must be severely condensed. The following may be taken as a brief resumé of present day opinion (_see_ Fig. 35):-- (1) In every case of chloroform administration, there is a fall of blood pressure. (2) If the drug be presented in weak concentration (less than 2 per cent. vapour strength), the fall is gradual and even (line AB). (3) If the same strength (say 2 per cent.) of vapour as produced the above effect be prolonged unduly, the respiration will cease at a time when blood pressure is still well above zero (line ABCB′). (4) The fall of pressure is due to diminished force of cardiac action, and at a later stage also to vaso-motor paresis. (5) The cessation of respiration is due partly to fall of blood pressure in the vessels supplying the medullary centre; partly to gradual poisoning of the centre itself by the drug. That the fall of B.P. in the cerebral vessels is in itself one explanation of the cessation of respiration, was proved many years ago by Leonard Hill in his inversion experiments. Just at the stage when respiration had ceased, the anæsthetic was withdrawn, and the animal inverted into the head-down position. The B.P. in the carotid at once began to rise, and natural respiration was resumed (line A′BCC′). The above conclusions refer to chloroform given in moderate vapour strength; other effects are produced if higher percentages are administered:-- (6) With high concentration of chloroform vapour, the fall of blood pressure is rapid, and is apt to become suddenly precipitous (line DD′).