Excellent accounts of the effects of dinitro-benzol in roburite factories have been published by Dr. Ross[228] and Professor White,[229] of Wigan. Mr. Simeon Snell[230] has also published some most interesting cases of illness, cases which have been as completely investigated as possible. As an example of the symptoms produced, one of Mr. Snell’s cases may be here quoted. [228] _Medical Chronicle_, 1889, 89. [229] _Practitioner_, 1889, ii. 15. [230] _Brit. Med. Journ._, March 3, 1894. [Illustration: Diagram of Visual Field.] C. F. W., aged 38, consulted Mr. Snell for his defective sight on April 9, 1892. He had been a mixer at a factory for the manufacture of explosives. He was jaundiced, the conjunctiva yellow, and the lips blue. He was short of breath, and after the day’s work experienced aching of the forearms and legs and tingling of the fingers. The urine was black in colour, of sp. gr. 1024; it was examined spectroscopically by Mr. MacMunn, who reported the black colour as due neither to indican, nor to blood, nor bile, but to be caused by some pigment belonging to the aromatic series. The patient’s sight had been failing since the previous Christmas. Vision in the right eye was 6/24, left 6/36, both optic papillæ were somewhat pale. In each eye there was a central scotoma for red, and contraction of the field (see diagram). The man gradually gave up the work, and ultimately seems to have recovered. It is, however, interesting to note that, after having left the work for some weeks, he went back for a single day to the “mixing,” and was taken very ill, being insensible and delirious for five hours. § 249. =The Blood in Nitro-benzol Poisoning.=--The effect on the blood has been specially studied by Huber.[231] The blood of rabbits poisoned by dinitro-benzol is of a dark chocolate colour, and the microscope shows destruction of the red corpuscles; the amount of destruction may be gathered from the following:--the blood corpuscles of a rabbit before the experiment numbered 5,588,000 per cubic centimetre; a day after the experiment 4,856,000; a day later 1,004,000; on the third day the rabbit died. [231] _Op. cit._ In one rabbit, although the corpuscles sank to 1,416,000, yet recovery took place. Dr. MacMunn[232] has examined specimens of blood from two of Mr. Snell’s patients; he found a distinct departure from the normal; the red corpuscles were smaller than usual, about 5 or 6 µ in diameter, and the appearances were like those seen in pernicious anæmia. Huber, in some of his experiments on animals, found a spectroscopic change in the blood, viz., certain absorption bands, one in the red between C and D, and two in the green between D and E; the action of reducing agents on this dinitro-benzol blood, as viewed in a spectroscope provided with a scale in which C = 48, D = 62, and E = 80·5, was as follows:-- [232] _Op. cit._