1888.] MICROSCOPICAL JOURNAL. 125 



arated by a bright green line. Upon the addition of a drop of a reducing 

 agent the character of the spectrum was immediately changed — the two 

 absorption bands became merged into one broad one ; but upon shaking up 

 the solution again with air, the former spectrum and bands immediately re- 

 appeared. This experiment tended to show that the taking up of the oxj'gen 

 was the result of chemical combination, and not of mere absorption ; or, in 

 other words, that in scarlet arterial blood the haemoglobin exists in the form 

 of oxyhtemoglobin, and in the dark-brown venous blood it is the presence of 

 reduced hcemoglobin that gives the characteristic color. 



Pedesis (Browniau MoTement).* 



By Prof. H. U. WHELPLEY. 



ST. LOUIS, MO. 



In 1837 an English physician and microscopist, by the name of Robert 

 Brown, described a peculiar motion of certain fine powders when suspended 

 in liquids. Under favorable circumstances he found that the smaller particles 

 would oscillate in a manner sugfgfestive of vital force. The doctor was not 

 the first person to obsei've this phenomenon, but he wrote so much about it 

 that it has since been quite generally known as the ' Brownian Movement.' 

 It has also been called the Brunonian movement, pedesis, non-vital motion, 

 and molecular movement. Prof. Bonders, of Leyden, was the first to observe 

 and record the movement. 



It occurs, according to references, when any of the following powders are 

 suspended in water: — carmine, vermilion, cobalt, wood charcoal, indigo, 

 camboge, pumice stone, carbonate of lead (flake white), glass; also in the 

 cr\'stals of the carbonate of lime that occur near the base of the spinal nerves 

 of a frog, the crystals from the iris offish, certain of the phosphates in urine, 

 the fat globules in milk, etc. I have not examined all of the crystals referred 

 to. but, in addition to the list of powders, I have experimented with prepared 

 chalk, Prussian blue, Paris gi'een, subnitrate of bismuth, oxide of zinc, pre- 

 cipitated phosphate of lime, oxide of magnesium, calomel, and carbonate of 

 zinc. I have specimens of the powders for inspection. Carmine gives the 

 most satisfactory results, although both Prussian blue and Paris green are 

 very active when first mixed with water. I found it difficult to observe the 

 movement of the fat globules in milk or cream. 



The cause of the motion is not known, and, in fact, very little has been said 

 or written about it. Most authors refer very briefly, if at all, to the phenom- 

 enon. Among the proposed explanations are currents in the liquids caused 

 by evaporation, changes of temperature, light, electricity, the eftect produced 

 by being confined between two glasses (a v.ery indefinite reason) , etc. Each 

 one of these theories has been contradicted. Where so many difler it is not 

 wise to put forth any great claim, but my observations lead me to the opinion 

 that perhaps the heat produced by the light from the mirror causes small cur- 

 rents that produce the motion. 



In order to observe the movement, all that is necessary is to mix the pow- 

 der with about 100 times its volume of water, and allow it to stand until all 

 the coarser particles have subsided. , With a pipette place a drop of the su- 

 pernatant liquid on a slide and cover with a thin cover glass. Examine with 

 an 1- inch or liigher power objective. It is quite necessary that the slide, 

 cover glass, objective, and ocular all be perfectly clean. I find that the mo- 

 tion is not simply an oscillation on one plane, but the particles move up and 

 down, as is shown by the changing of focus as they move. 



• Abstract of a paper read before the St. Louis Club of Microscopists, Juue 5, 1888. 



