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the blood of vertebral animals, careful investigations into the struc- 

 ture of the ductless glands, and several experiments, he deduced the 

 follawing conclusions : — 



1. That the blood corpuscles of vertebrate animals are originally 

 formed in the lymphatic glandular system, and that the great ma- 

 jority of them on joining the circulation, become coloured in a man- 

 ner that is as yet unexplained. Hence, the blood may be considered 

 as a secretion from the lymphatic glands, although in the higher 

 animals that secretion only becomes fully formed after it has received 

 colour by exposure to oxygen in the lungs. 



2. That in the mammalia, the lymphatic glandular system is com- 

 posed of the spleen, thymus, thyroid, supra-renal, pituitary, pineal, 

 and lymphatic glands. 



3. That in fishes, reptiles, and birds, the coloured blood corpuscles 

 are nucleated cells originating in these glands, but that in mammals, 

 they are free nuclei, sometimes derived as such from the glands, at 

 others, developed within colourless cells. 



4. That in certain hypertrophies of the lymphatic glands, their 

 cell elements are proportionally increased in number, and under such 

 circumstances the colourless cells of the blood are also proportionally 

 increased. This is Leucocythemia. 



5. That the solution of the corpuscles of the blood, conjoined with 

 the effete matter derived from the tissues, which is not converted 

 into albumen, constitute blood fibrin. 



2. On the Mechanical action of Radiant Heat or Light : 

 On the Power of Animated Creatures over Matter : 

 On the Sources available to Man for the production 

 of Mechanical Effect. By Professor William 

 Thomson. 



On the Mechanical Action of Radiant Heat or Light. 

 It is assumed in this communication that the undulatory theory 

 of radiant heat and light, according to which light is merely radiant 

 heat, of which the vibrations are performed in periods between cer- 

 tain limits of duration, is true. " The chemical rays," beyond the 

 violet end of the spectrum, consist of undulations of which the full 

 vibrations are executed in periods shorter than those of the extreme 

 visible violet light, or than about the eight hundred million millionth 



