Imatges de pàgina
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or 2400 grains. It was first filled with cold water, which, when its temperature had been ascertained, was thrown into the receiver before used; it was next filled with hot water of temperature about 110, so that the heat of the glass might be nearly the same as that of the blood: and lastly, when the vein or artery had been opened, the bottle was immediately emptied and filled with blood, the temperature of which was ascertained by the thermometer in less than a quarter of a minute. The

a mixture now was instantly made, and by the same thermometer the highest temperature after mixture was discovered.

The four following trials were made on the blood of two lambs, both about five inonths old. The temperature of the air was 60.

Cold water 57.5. Venous blood 100. Mixture 80; after one minute 78.5.

Water 58. Arterial blood 103. Mixture 80; after one minute 79.

Water 58. Venous blood 101.5. Mixture 79; after one minute 78.25.

Water 58. Arterial blood 106.5. Mixture 81; after one minute 80.

The rate of cooling was not noticed after the first minute had elapsed, as the blood then generally began to coagulate. The specific gravity was only ascertained in the two last trials; that of the venous blood was found to be 1050, and that of the arterial 1049; and hence allowing, as before, one degree of the cooling effect to be produced by the receiver, the capacity of venous blood for heat appears to be •852, and that of arterial blood •839.

It is evident that these trials admit of less accuracy than the preceding; and much more confidence, it appears to me, is due to the third series of experiments; so that, if required, I should be inclined to give the numbers thence deduced, as the greatest approximation to the truth.

2. On the comparative Temperatures of venous and arterial

Blood, and of different Parts of the animal Body. To endeavour to ascertain the comparative temperature of venous and arterial blood, I have made a considerable number of experiments; some of which on lambs, sheep, and oxen, it

4.

will be sufficient for me in this place to describe. In each instance, a long incision was made through the integuments; the jugular vein was laid bare, and the exact seat of the carotid artery found. The vein was then opened, and a small delicate thermometer introduced, and thrust about an inch up the vessel beyond the wounded part; and as the bulb of the instrument was small, the flow of blood was not stopped. When the mercury was stationary, its height was marked. The carotid artery next was divided, and the thermometer was immersed in the current of blood, and left there till it ceased to rise.

The following are the results of five experiments made on lambs, all of which were about three months old. The thermometer in the shade stood at 65.

1. Venous blood 102.5 Arterial blood 104
2.
104

105
3.
104

105
103.5

105
5.
104

105 The following results were obtained from three experiments on sheep, whose exact age I could not ascertain. The thermometer in the shade was 60.

1. Venous blood 103.5 Arterial blood 104.5
2.
102.5

104
3.
103

104 The experiments on oxen were only two in number. The temperature of the air was 64.

1. Venous blood 100 Arterial blood 101.5
2.
100

101 In both instances the oxen were knocked down before the vessels were opened; and as respiration had ceased in consequence of the injury of the brain and spinal cord, no difference of colour, of course, was perceptible between the blood from the jugular vein and that from the carotid artery.

These results, so different from what might have been expected, from the observations of Messrs. Coleman and Cooper on the temperature of the two sides of the heart, led me to repeat their experiments. The experiments in which I place most confidence were made on lambs about four months old, and to these I shall confine myself at present. In each instance the animal was killed by the division of the great vessels of the

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neck; an opening was made immediately into the thorax, and a very delicate thermometer was introduced into the ventricles of the heart by means of a small incision. The operation occupied so short a space of time, that in three instances the right auricle had not ceased contracting.

1. Venous blood. 104 Left .... ... 106

Arterial ... 105.5 3. Rectum .. 105
Rectum ..... 104 Right ventricle . 105.5
Right ventricle 105.5

Left ...

106.5
Left ... 106 4. Rectum .. 105
2. Rectum ...

105

Right ventricle . 106 Right ventricle 105 Left ......... 107 I cannot well explain the difference which exists between the results of the preceding experiments, and those of Messrs. Coleman and Cooper, which are directly opposite. Can the mode in which the animals they experimented on were put to death, be the cause of the want of agreement? In death by asphyxia, there is generally an accumulation of blood in the right ventricle; and in many instances I have observed, when the right ventricle has been distended with blood, little difference of temperature between the two sides of the heart.

To describe all the experiments that I have made to ascer. tain the temperature of different parts of the animal body, would extend this paper to an unusual length, and there is the less occasion for a long description, as the comparative results were very similar. It will be sufficient therefore here to notice the observations made on the human body, and on that of a lamb.

That the thermometer might be equally applied to all parts of the surface, its bulb, in form Dearly cylindrical, was fixed to a small piece of cork, hollowed and lined with fine wool, and thus half its superficies was applied in each instance. The observations were made on the naked body at seven A. M. immediately after quitting bed. The temperature of the air of the room was 70. The following were the results obtained:

At the central part of the sole of the foot ........ 90

Between the malleolus internus and the insertion of the tendo Achillis, where the artery is felt .

93 Over the middle of the tibia ...

91.5 On the middle of the calf...

93

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91

Over the popliteal artery at the bend of the knee ... 95
Over the femoral artery in the middle of the thigh .. 94
Over the middle of the rectus muscle
Over the great vessels in the groin

96.5 About a quarter of an inch below the umbilicus .... 95

Over the sixth rib on the left side where the heart is felt pulsating ...

94 Over the same place on the right ..

93 Under the axilla, the whole surface of the bulb being applied .....

98 About an hour had now elapsed from the commencement of the experiment. The thermometer again applied to the sole of the foot rose no higher than 85, five degrees less than at first. A disagreeable sensation of cold was experienced, and particularly in those parts not supplied with large vessels, and out of the course of the great arteries. The body remained unpleasantly chilly till breakfast had been taken, and then a slight degree of pyrexia was perceived; the heat of surface being increased, the pulse quickened, and the mouth slightly parched. After breakfast, the thermometer was applied to both hypochondriac regions, and the left was found one degree higher than the right.

To ascertain the temperature of different parts of the surface beneath the integuments, the bulb of a thermometer was introduced through small incisions about half an inch between the skin and subjacent parts of a lamb just dead. The heat of the rectum was first ascertained, as a mean of marking the rate of cooling, and the different parts were then tried in the following order:

Venous blood in the jugular vein .... 105.5
Arterial blood from the carotid artery 107
Rectum

105.5
Over the metatarsal bone.

97 Over the tarsal bone

90 Over the knee joint

102 About the head of the thigh

103 At the groin.

... 104 Nearly a quarter of an hour had been occupied in making these observations, and the temperature of the rectum was now

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found to be 105. The three great cavities were next opened in the order enumerated.

Near the lower part of the liver . . 106
The substance of the liver . . . . . 106.5
The substance of the lung . 106.5
The left ventricle

107
The right ventricle ..

106 The central substance of the brain 104 Rectum ..

... 104.5 Surprised at the temperature of the brain being lower than that of the rectum, I was led to repeat the experiment. It may be proper to notice a few of the results, as it is a curious circumstance which they confirm. The four experiments I shall mention were made on lambs. As soon as the animal was dead, the cranium was perforated, and a delicate thermometer introduced into the central part of the brain. 1. Brain 104

Rectum 104.75 2. Brain 104.75

Rectum 105.5 3. Brain 105.5

Rectum 106.5 4. Posterior part of the brain 105.5; anterior 103.

Rectum 106•5. The temperature of the air at the time was 68. Different parts of the brain were found to vary considerably in temperature; the anterior, as already noticed, being lower than the posterior, and the superficial than the deep-seated parts.

3. Remarks and Conclusions. That there is no material difference between venous and arterial blood in respect to specific caloric, excepting what arises from difference of specific gravity; that the temperature of arterial blood is higher than that of venous; and the temperature of the left side of the heart, than that of the right; and lastly, that the temperature of parts diminishes as the distance of the parts from the heart increases--are the general results of the preceding experiments.

Admitting the accuracy of these experiments, and I think that they will be found correct when repeated, what are their consequences in a theoretical point of view?

They are evidently in direct opposition to Dr. Crawford's hypothesis; the essence of which is, that the capacity of arterial

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