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The ordinary effects of cold on the skin locally and the system generally will not be mentioned here； except to add the remark of Captain Wood that in Greenland； among his party； could be seen ulcerations； blisters； and other painful lesions of the skin。 In Siberia the Russian soldiers cover their noses and ears with greased paper to protect them against the cold。 The Laplanders and Samoiedes； to avoid the dermal lesions caused by cold （possibly augmented by the friction of the wind and beating of snow）； anoint their skins with rancid fish oil； and are able to endure temperatures as low as …40 degrees F。 In the retreat of the 10；000 Xenophon ordered all his soldiers to grease the parts exposed to the air。
Effects of Working in Compressed Air。According to a writer in Cassier's Magazine； the highest working pressures recorded have been close to 50 pounds per square inch； but with extreme care in the selection of men； and corresponding care on the part of the men； it is very probable that this limit may be considerably exceeded。 Under average conditions the top limit may be placed at about 45 pounds； the time of working； according to conditions； varying from four to six hours per shift。 In the cases in which higher pressures might be used； the shifts for the men should be restricted to two of two hours each； separated by a considerable interval。 As an example of heavy pressure work under favorable conditions as to ventilation； without very bad effects on the men； Messrs。 Sooysmith & Company had an experience with a work on which men were engaged in six…hour shifts； separated into two parts by half…hour intervals for lunch。 This work was excavation in open； seamy rock； carried on for several weeks under about 45 pounds pressure。 The character of the material through which the caisson is being sunk or upon which it may be resting at any time bears quite largely upon the ability of the men to stand the pressure necessary to hold back the water at that point。 If the material be so porous as to permit a considerable leakage of air through it； there will naturally result a continuous change of air in the working chamber； and a corresponding relief of the men from the deleterious effects which are nearly always produced by over…used air。
From Strasburg in 1861 Bucuoy reports that during the building of a bridge at Kehl laborers had to work in compressed air； and it was found that the respirations lost their regularity； there were sometimes intense pains in the ears； which after a while ceased。 It required a great effort to speak at 2 1/2 atmospheres； and it was impossible to whistle。 Perspiration was very profuse。 Those who had to work a long time lost their appetites； became emaciated； and congestion of the lung and brain was observed。 The movements of the limbs were easier than in normal air； though afterward muscular and rheumatic pains were often observed。
The peculiar and extraordinary development of the remaining special senses when one of the number is lost has always been a matter of great interest。 Deaf people have always been remarkable for their acuteness of vision； touch； and smell。 Blind persons； again； almost invariably have the sense of hearing； touch； and what might be called the senses of location and temperature exquisitely developed。 This substitution of the senses is but； an example of the great law of compensation which we find throughout nature。
Jonston quotes a case in the seventeenth century of a blind man who； it is said； could tell black from white by touch alone； several other instances are mentioned in a chapter entitled 〃De compensatione naturae monstris facta。〃 It must； however； be held impossible that blind people can thus distinguish colors in any proper sense of the words。 Different colored yarns； for example； may have other differences of texture； etc。； that would be manifest to the sense of touch。 We know of one case in which the different colors were accurately distinguished by a blind girl； but only when located in customary and definite positions。 Le Cat speaks of a blind organist； a native of Holland； who still played the organ as well as ever。 He could distinguish money by touch； and it is also said that he made himself familiar with colors。 He was fond of playing cards； but became such a dangerous opponent； because in shuffling he could tell what cards and hands had been dealt； that he was never allowed to handle any but his own cards。
It is not only in those who are congenitally deficient in any of the senses that the remarkable examples of compensation are seen； but sometimes late in life these are developed。 The celebrated sculptor； Daniel de Volterre； became blind after he had obtained fame； and notwithstanding the deprivation of his chief sense he could； by touch alone； make a statue in clay after a model。 Le Cat also mentions a woman； perfectly deaf； who without any instruction had learned to comprehend anything said to her by the movements of the lips alone。 It was not necessary to articulate any sound； but only to give the labial movements。 When tried in a foreign language she was at a loss to understand a single word。
Since the establishment of the modern high standard of blind asylums and deaf…and…dumb institutions； where so many ingenious methods have been developed and are practiced in the education of their inmates； feats which were formerly considered marvelous are within the reach of all those under tuition To…day； those born deaf…mutes are taught to speak and to understand by the movements of the lips alone； and the blind read； become expert workmen； musicians； and even draughtsmen。 D。 D。 Wood of Philadelphia； although one of the finest organists in the country； has been totally blind for years。 It is said that he acquires new compositions with almost as great facility as one not afflicted with his infirmity。 〃Blind Tom；〃 a semi…idiot and blind negro achieved world…wide notoriety by his skill upon the piano。
In some extraordinary cases in which both sight and hearing； and
sometimes even taste and smell； are wanting； the individuals in a most wonderful way have developed the sense of touch to such a degree that it almost replaces the absent senses。 The extent of this compensation is most beautifully illustrated in the cases of Laura Bridgman and Helen Keller。 No better examples could be found of the compensatory ability of differentiated organs to replace absent or disabled ones。
Laura Dewey Bridgman was born December 21； 1829； at Hanover； N。H。 Her parents were farmers and healthy people。 They were of average height； regular habits； slender build； and of rather nervous dispositions。 Laura inherited the physical characteristics of her mother。 In her infancy she was subject to convulsions； but at twenty months had improved； and at this time had learned to speak several words。 At the age of two years； in common with two of the other children of the family； she had an attack of severe scarlet fever。 Her sisters died； and she only recovered after both eyes and ears had suppurated； taste and smell were also markedly impaired。 Sight in the left eye was entirely abolished； but she had some sensation for large； bright objects in the right eye up to her eighth y