Ottolenghi also found colour-blindness very rare; he met with one case (green-blindness) among 460 criminals tested with Holmgren’s wools. This result also corresponds with examinations of lower races, such as Samoyeds, Lapps, Esquimaux, Nubians, etc. It should be added that this result also needs confirmation, as it does not correspond with other observations. Thus Holmgren found that colour-blindness existed in 5.60 per cent. of 321 criminals, while among 32,000 of the ordinary population the proportion was scarcely 3.25 per cent. Dyschromatopsia has been found common, a fact of great significance, since this disorder is so frequently connected with grave disturbance of the nervous system. The healthiness of eye in criminals, if confirmed, may be compared with a similar condition in imbeciles. In a study of twenty young adult male imbeciles of a minor degree than idiocy, Dr. Oliver found vision normal and colour perception apparently normal, and the eyes singularly free from the slight morbid changes so common in the eye. This condition, “which is shown by a proper balance of muscular action, a persistence of congenital hypermetropia, and an abnormally healthy appearance of the eye-ground (presenting a picture that is almost identical to the one seen during infantile existence), may be considered as significant of a type of unused, healthy, adult human eye.”[46] The hearing of criminals is relatively obtuse, and they are prone to disease of the ear. Thus Dr. Gradenigo, at the request of Lombroso, undertook a series of researches into the matter,[47] in 110 instinctive and occasional criminals. Of the 82 criminal men he examined, 55 (67.3 per cent.) proved to be inferior to the normal. Of these 82, there were 40 who were instinctive criminals, and of these 29 (72.5 per cent.) had defective hearing. Of the 28 women, 15 (53.5 per cent.) possessed hearing inferior to the normal. Four of the women, however, possessed hearing much superior to the normal average.[48] Gradenigo found that the defective hearing was due in the great majority of cases to inflammatory affections of the middle and internal ear. He found no constant relation between defective hearing and obtusity of touch, taste, and smell, frequently found among criminals.