whereas, it appears that some agencies which are not luminous materially influence the phenomena of vegetable vitality.

Without entering into any discussion in this place on the probable existence or otherwise of a principle distinct from light and heat in the sun's rays, to which we refer the curious chemical changes produced by solar influence, it will be sufficient to admit the existence of three distinct classes of phenomena which can not, I think, be disputed.

These are luminous influence-light; calorific power-heat; and chemical ex

citation-actinism.

The problem which these researches were directed to solve was the proportion and kind of influence exerted by light, heat, and actinism-as the principle supposed to be active in producing the chemical phenomena of the solar rays has been called-in the various. stages of vegetable growth.

The means we have of separating these phenomena from each other are not very perfect; indeed, in the present state of our knowledge, it is impossible to have evidence of the operations of either light, heat, or actinism, absolutely separate from each other.

If we

use the prismatic spectrum, we have over every portion of it a mixture of effects. Even in the mean yellow, or most luminous rays, we have a considerable amount of thermic action, and, under some circumstances, evidence of chemical power. In the violet rays, which have been particularly distinguished as chemical rays, we have light and heat, and in the calorific rays

we have decided proof of both luminous and actinic power. Experiments show with the prismatic spectrum that we have, in fact, no certainty, that the results due to a particular ray—that ray being regarded as the representative of a particular phenomenon—are not the combined effect of the three forces. The same objections apply to absorbent media, but the amount of each influence is readily determined; and we are therefore enabled to refer fore enabled to refer any particular result to a tolerably well defined agency.

Before the British Association these facts were made very clear by a large number of exceedingly interesting crucial experiments, and all were embodied in a report thereon. They showed that under the action of those radiations which have permeated variously colored media, such as tinted glass and colored, transparent fluids, it was not sufficient to state that a yellow, red, or blue glass or fluid was employed, as it by no means followed that these media are permeated only by the rays corresponding in color, or by the influences due to a given order of refrangibility.

The difficulties which oppose themselves to experiments made with colored media have been strongly felt by other observers.

Dr. Dauberry says in his memoir, "On the Action of Light Upon Plants, etc." "The difficulty, however, of comparing the relative intensity of the light transmitted by the variously colored media, which were employed in my experiments, induces me to content myself with showing that the effect of light upon plants corresponds with

its illuminating rather than with its chemical or calorific influence; and to waive the more difficult inquiry, whether its operation upon the vegetable kingdom exactly keeps pace with the increase of its own intensity."

In 1842 and 1844 Robert Hunt again reported before the British Association the following which are the facts:-He stated the kind of examination to which he then subjected each colored screen-"Many effects which which have from time to time presented themselves, have convinced me of the necessity of a still more close examination of the order in which radiant principles permeate the media employed. I have, therefore, in every case examined with all care the illuminating, calorific, and chemical effects of the solar rays which have passed the media employed. The amount of light has been determined by measuring off, in parts of an inch, the prismatic rays which pass the screen. This is preferable to any system of measuring which depends upon the power of the eye to appreciate either light or shadow. Having formed a well defined spectrum on a white tablet, and carefully worked off the center of the yellow ray as being the point of maximum light, and the limits of each. of the other rays, the transparent colored medium was interposed and the amount of absorption observed. These examinations, many times repeated, were made with reference to the luminous rays only; and, in the description of my experiments, I shall, considering the unabsorbed ray as being represented by 100, express the amount of

light actually effective by such a number as may give the sum of the rays measured off after permeation."

The calorific influences which escape absorption, and which have been determined by the expansion of the mercury in a thermometer with a blackened bulb, placed behind the colored glass or fluid, and by the evaporation of ether from a sheet of blackened paper, as recommended by Sir John Herschel, will be expressed numerically in the same way as light, without reference to the color of any ray. I am far from considering the thermic influences of the solar rays as quite independent of the color of the ray with which they may be associated; but in these experiments on plants, it appears to me, we can only deal satisfactorily with the total amount of radiant heat which is active under the conditions of the experiments, the terrestrial heat being in all comparative experiments the same."

It has, indeed, been shown by Dr. James Stark' by direct experiments, and indirectly by other observers, that color exerts a very powerful influence in the conduction, radiation and permeation of heat. Following up some of these experiments both from a scientific and therapeutic point of view myself, I found that tuberculous patients derive the best results by either wearing white garments over the entire body or in a perfectly nude state. This mode of treatment I have followed since 1890. and never since then has this method depreciated in my judgment, even one

per cent.

(TO BE CONTINUED.)

tricuspid regurgitation?

2. Give the etiology, symptomatology, diagnosis, and prognosis of capillary bronchitis.

3. What do you understand by: Borborygmus; aerophagy; gastroptosis: ascites; brachycardia; chlorosis; hematuria.

4. Write an article, not to exceed one hundred words, on arthritis defor

mans.

5. Describe a case of psoriasis. 6. In parallel columns give the distinguishing points of chickenpox, 7. How would you distinguish a case smallpox and measles.

8. Give briefly the pathology and symptoms of infantile spinal paralysis; i.e., atrophic spinal paralysis.

9. a. What is the normal pulse rate of a child one year old?

b. What is the reaction of saliva?

c. What is the reaction of the gastric juice?

d. What is the reaction of the blood? e. What is the reaction of the normal urine?

f. What is the specific gravity of normal urine?

10. Describe a typical case of cerebral hemorrhage.

causation.

I. What are the various diameters of the inlet and outlet of the pelvis? 2. What are the signs of pregnancy?

3. What changes occur in the genital organs during pregnancy?

4. Describe the fetal heart sounds, their rate, when and where best heard.