This investigation was performed to clarify what kind of relationship might be presented between various environmental factors and horse skin temperature in the course of the year. As a result, some new findings were obtained. Skin temperature was measured on 253 healthy horses at 28 spots on the left side of each horse by using the electro-thermometer. At the same time, recording was made on the conditions of weather, atmospheric pressure, humidity, and ambient temperature. 1) The skin temperature, as measured, was not so much influenced weather, atmospheric pressure, or humidity, but affected chiefly by ambient temperature. 2) The effect of ambient temperature on skin temperature was marked at the spots of the leg slight at those of the trunk, and little or none at those of the dock and heart region. 3) Skin temperature was higher at the trunk than at the leg. It was the highest at the dock in the body. There was a tendency that the closer was a spot of the leg to the wall of the hoof, the lower became skin temperature at the spot. 4) The difference in skin temperature between any two spots of measurement was relatively great under low ambient temperature and relatively small under high ambient temperature.

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Electrocardiographic studies were conducted on 6 horses subjected to partial immersion in a hot spring. These horses had been accustomed to entering the bath. They were held in a bath at 38-40°C for 30 minutes, at 40-43°C for 1 hour, and at 43-45°C for 30 minutes in experiments 1, 2, and 3, respectively. Bipolar electrocardiograms (from the apexbase lead) were recorded before bathing, immediately after, and 30 minutes after the end of bathing, as well as during bathing. In experiment 1, the heart rate remained unchanged or decreased slightly during bathing. It increased slightly immediately after bathing probably due to a slight exertion associated with getting out of the tub. In experiments 2 and 3, the heart rate increased progressively to sinus tachycardia over the period of bathing. It decreased immediately after the end of bathing. These results suggest that the bathing in hot water may be more effective in causing cardiac acceleration than the exertion associated with getting out of the tub. Before bathing, the T-wave had a diphasic (negative-positive) configuration. Immediately after bathing in experiment 1, the negative component decreased and the positive component increased slightly in amplitude. During the corresponding period in experiments 2 and 3, the T-wave became monophasic and positive, with an amplitude 2 to 3 times as high as that during the pre-bathing period. In experiment 1, a second-degree A-V block was observed in 2 horses during bathing . In experiments 2 and 3, the A-V block which had been observed before bathing, disappeared during bathing. From the presence of slight bradycardia and A-V block in experiment 1, it is suggested that the water temperature of 38-40°C may induce vagotonia. The occurrence of tachycardia and the disappearance of A-V block in experiments 2 and 3 may suggest that the water temperature of 40-45°C induces sympatheticotonia and reduction of vagal tone. The practice for race horses to bathe in water at 38-40°C for 2034 minutes at the hotspring sanitarium may cause vagotonia on account of its soothing effect on the horse. A water temperature of 40-45°C seemed to have no adverse effect on normal horses. Care should be teken, however, in bathing a horse in water at this temperature, if the horse is suspected to have an abnormality in the cardiac function.

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The estimation method for equine plasma alkaline phosphatase was modified with regard to the optimal conditions of pH, substrate concentration and concentration of magnesium ion. And thus estimation method employed under optimal conditions was proved to be excellent compared with original one .

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It was previously reported by the author that an abnormal severe transition of iron has been recognized in the body of a horse infected with equine infectious anemia (ETA). In this horse, a large number of tissue cells of the spleen were destroyed severely after in fection with ETA. Then, the storage iron was spilt from the destroyed tissue cells into the circulating blood. In the case of ETA, most siderocytes were produced from the cells which had been originated from tissue and blood and which had absorbed ferritin and hemosiderin as storage iron. Consequently, it was clearly understood what was the mechanism of for mation of siderocytes which had been detected in the peripheral blood of a horse infected with ETA. If the above-mentioned results are always obtainable, a difference will be found in the iron figure of the siderocyte between the acute case of ETA which has severely destroyed tissue cells and in which a large quantity of iron has been spilt into the blood stream, and the chronic case which has only slightly destroyed tissue cells and in which a small quantity of iron has been spilt in the blood stream. Therefore, comparative investigation was carried out on the iron figure of the siderocyte between the acute and chronic case of ETA. The siderocytes were morphologically divided into the following three types by iron figure : (a) FG type which had granules stained blue owing to the presence of hemosiderin and contained in the cytoplasm, (b) FD type which had cytoplasm diffusely stained blue owing to the presence of ferritin, and (c) FGD type which had cytoplasm diffusely stained blue and containing granules stained blue owing to the presence of ferritin and hemosiderin. When investigation was made in an acute case and two chronic cases of ETA, the FG type was abundantly found in the acute case andthe FD type in the chronic cases. In short, it was recognized that there was a difference in the iron figure of the siderocyte between cases produced by different pathogenesis of ETA.

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A race horse 3 years and a half old suddenly died. It was found to have been suffering from coronary aneurysm accompanied by rupture, and was studied formal-pathogenetically. The aneurysm was shown in the right coronary artery at a portion transitional to its descending branch. The results of this investigation essentially lend support to the neurogenic theory which has been asserted by one of the authors, SATOH, and his associates from their studies on so-called idiopathic rupture of the aorta in an aged stallion. The histopathologic findings in the wall of the affected portion of the coronary artery were represented by an extensive hydropic medial degeneration. This change was regarted as a result of the primary continuous edmatous process (disturbance of water metabolism), which had been caused by "microvascular alteration" (edematous loosening and swelling of the wall) of the vasa vasorum of the artery. In conclusion, it seems that the "microvascular alterations" were caused by neurogenic changes : there were organic nervous disturbances in the adventitia of the aneurysm-affected portion of the coronary artery. Formal-pathogenetically, it was understood that extensive hydropic medial degeneration was a factor necessary for the occurrence of aneurysm and rupture. The wall of the coronary artery became thin and rarefied as a result of medial degeneration. Accordingly, this change would bring about the dilation and the rupture, which might be accelerated by blood pressure or the partial.

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Until recently intravenous anesthesia had been an almost exclusive type of equine general anesthesia. Equine inhalation anesthesia, however, has been used again in practice since ten years ago with the advancement of the premedication method and the development of powerful inhalation anesthetics, such as halothane. The practical use of halothane as anes thetic has been reported by many investigators, but no data are available on the inhaled concentration of halothane-oxygen which is used for induction and maintenance. Experiments were carried out with 30 Thoroughbred horses to determine the concent ration and amount of halothane and the anesthetic period for the practical use of this drug for induction and maintenance. An anesthetic apparatus under the closed circuit cycle system was employed. The inhaled concentration was measured by a “Fluothane-meter” throughout the anesthetic period. Every horses was administered with diazepam and atropine sulfate as a premedicant. Succinylcholine chloride was used to cast the horse. An endo-tracheal tube with a cuff was inserted through the oral cavity as soon as the horse lay down. The following results were obtained. 1. Anesthesia was induced with halothane-oxygen from 6 to 12 minutes, or its mean was 8 minutes. 2. The peak concentration of halothane was between 1.80 and 3.15 percent, or 2.45 percent on the average, during the induction period. The amount of halothane used during this period was from 18 to 47 ml, or 31.6 ml on the average. For the maintenance of anesthesia it was required to use a period of 47-140 minutes, 15-58 ml of halothane, and a halothane concentration of 0.8-2.0 percent, or 76.2 minutes, 31.2 ml, and 1.23 percent, respectively, on the average. 4.The recovery period varied from 10 to 85 minutes ; its mean was 31 minutes. The length of anesthesia had influence upon that of the recovery period. 5.For the maintenance of anesthesia it was required to administer 2.81-8.33 ml of halothane per 100 kg of body weight. The amount of halothane to be used per 100 kg of body weight decreased according to an increase in body weight and maintenance period.

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The bromsulphalein clearance test was applied to 10 healthy horses and a horse in which liver dysfunction was artificially induced by oral administration with carbon tetrachloride.The following results were obtained .1)The normal bromsulphalein clearance T 1/2 value was 3 .5±0.42 minutes when determined by a method in which 1 g of bromsulphalein intravenously had been injected .2)The bromsulphalein clearance T 1/2 value reached an abnormal maximum value (6 .51 minutes) after 24 hours in the horse administered with 0 .4 ml/kg of carbon tetrachloride. In this horse, that value changed as well as the value of serum indirect bilirubin and serum glutamic oxalacetic transaminase. These values varied with the degree of liver dysfunction.3)No harmful signs were manifested by these horses injected bromsulphalein dye. From these results, it is believed firmly that the bromsulphalein clearance test is an appropriate method to determine the liver function, such as secretion and excretion.

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