2
1093 give rise to outward and visible signs such as agglutination and precipitation, altered rate of coagulation, increased or decreased viscosity, and the like: and every one of them has been made the basis of a clinical laboratory test. In the current number of the .B’rs7! Jounzal of Tuberculosis Dr. A. Westergren, of Stockholm, describes briefly the" stabilitary " reaction of blood which depends on the rate of sedimentation of red blood corpuscles in a column of withdrawn citrated blood. Briefly, the test i is as follows. The blood is withdrawn from the patient’s I vein by means of a syringe having one-fifth of the barrel filled with 3’8 per cent. sodium citrate solution. When the remaining four-fifths have been filled with patient’s blood the contents are immediately emptied into a small test-tube and well mixed. The mixed blood is then drawn into a pipette-tube 30 cm. long (with an inner diameter of 2’5 mm.) up to a height of 20 cm. and placed in a rack. The time is noted, and the tube allowed to stand for 1, 2, and 24 hours, when the test is read off by measuring the height of the layer of plasma in millimetres from the lower meniscus of the free surface to the upper border of the deposited blood corpuscles. In blood drawn from healthy men the top layer of clear plasma at the end of one hour is said to be 2 mm. and in women 5-10 mm. An increased sedimentation (i.e.. a reduced suspension stability of the blood) is found in pregnancy and in acute infectious diseases, especially when associated with much pyrexia. Dr. ’, Westergren finds that this increased sedimentation is markedly shown in cases of acute pulmonary tuber- culosis. He says: " No single test of an active or probably active case has given a normal value, and no case which must be considered quite benign, and certainly shows no signs of activity, has given a high, even a middle-high, figure." He therefore considers, the reaction to be a more reliable measure of activity than is a temperature record. The reaction is, of course, in no way specific, and can only have a relative value in estimating activity as an aid to diagnosis and prognosis. A full account of this reaction is given in English in 4c. 3[end. Scdndi7za.vica, Vol. LIV., pp. 247-281. - SO-CALLED SNOW-BLINDNESS. SolE interesting notes regarding the pathological effects of the visible and invisible spectrum on the eye, more especially in relation to snow-blindness, are contributed by Mr. Arthur W. Ormond in the April number of Guy’s Hospital Reports. These make it plain that both visible and invisible rays can produce definite pathological effects on the ocular tissues, but further inquiry is required to prove the exact wave-lengths which set up these changes. The heavy incidence of cataract in glass-workers-exposed as they are to the intense heat and brilliant illumination of molten glass-led to the suggestion that the heat rays are the cause of the injury in these cases, and the balance of opinion appears to be in favour of this hypothesis. However, more recent experiments suggest that lenticular changes may be produced by ultra-violet radia- tions. The effects of sunburn are probably due not to visible but to ultra-violet rays. Meantime, we have some interesting first-hand observations by a young officer, a member of a Canadian Arctic expedition, who visited Parry Archipelago and its neighbourhood. To begin with, it is suggested that snow-blindness is a bad term, as the victim is not blind." The condition was never experienced in extremely low temperatures and seldom at freezing point, but generally in a condi- tion of mist or fog, a fog-haze or "white-darkness" " in snow-covered regions when all sense of perspective and stereoscopic vision is lost. Bright sunlight affected the eyes in a different manner, and real blindness was never the result of bright glaring sunlight and shadow. The symptoms of severe conjunctivitis and superficial ulceration of the cornea were pronounced, " grittiness," discharge from eyes and nose, in 24 hours intense local pain-lasting sometimes for 10 or 12 hours-the pain being described as the sensation of thousands of red-hot needles being forced through the eyes to the sockets. The eyeballs and lining of the lids are covered by a greyish film, through which the iris and pupils are just discernible. The sufferer can see nothing, even with the eyes held open. If the eyes are protected by bandages at the first noticeable symptoms, after three days the eyes are practically normal, but there is a tendency to relapse if unfavourable condi- tions recur. The use of dark or coloured glasses is sufficient protection, but the leader of a party cannot always keep glasses before his eyes; the glasses become dimmed with hoar-frost and have to be removed to be cleaned. The native Eskimos are not immune from attacks of snow-blindness, and Scott and Shackleton observed that dogs and ponies manifested characteristic symptoms. The Eskimo has learned to recognise weather conditions which are dangerous from this point of view and arranges his travels accordingly. When he does travel-rarely more than five miles a day-he protects his eyes with horizontally slotted wooden spectacles cut from soft drift timber ; even these are not absolutely preventive. Nansen records that in his Polar expedition only two of his party, who had neglected the necessary precautions, suffered from snow-blindness. As to the part of the spectrum responsible for the sensations experienced by the victim, we may exclude the infra-red rays ; nor is the visible spectrum entirely responsible, for in the tropics, where light is very intense, symptoms such as these are not experienced, and in summer there is no complaint of " snow-blind- ness " amongst ordinary Swiss tourists. Fuchs, of Vienna, records that some visitors to the Alps after exposure to the snowfields " see red," espe- cially in a dimly illuminated room. The question remains whether snow-blindness can be due to ultra- violet rays alone. During the war an a,cute condition of the eyes similar to snow-blindness was set up in persons working with a searchlight device elaborated for signalling at sea, whereby all parts of the spectrum except the ultra-violet and a few red rays were filtered out. The effects seem to be due not so much to the quality as to the quantity of these rays. A few of the short rays may penetrate to the lens, but experi- ment shows that very few ultra-violet rays reach as far as the retina. Retinal symptoms are not amongst those caused by snow-blindness. The glass made by Sir William Crookes for " goggles" to prevent blindness, which transmits the greatest amount of light and the smallest proportion of ultra-violet rays, effectively combats the source of irritation. But the luminous rays of the spectrum under certain conditions may also produce pathological effects ; "in the slighter cases there is recovery, but in some cases the scotoma is permanent. Some thoughtless people found this out to their cost during the recent partial eclipse of the sun. SOME CONDITIONS AFFECTING THYROID ACTIVITY. ACCORDING to W. B. Cannon and P. E. Smith, of the Harvard Medical School,l gentle massage of the thyroid of a cat for two or three minutes causes an increased rate of the denervated heart, amounting in some instances to 33 per cent. over the basal rate. The development of the maximal increase of rate is usually slow, requiring 30 to 60 minutes, and its diminution is also slow. This augmentation of heart-rate caused by thyroid massage occurs in the absence of the adrenal glands. Stimulation of the cervical sympathetic trunk as it leaves the ganglion stellatum induces a similar augmentation of the denervated heart, but this does not occur if the thyroid gland has been previously removed. If the cardiac fibres from the stellate ganglia are severed, as well as the vagus nerves and an afferent nerve, such as the sciatic or brachial, is stimulated under a degree of anaesthesia which will permit of reflex contraction of the nictitating membrane and dilatation of the pupils, there is a primary increase of rate due to adrenal secretion, 1 Endocrinology, iv., 1920.
