762 



THE POPULAR SCIENCE MONTHLY. 



about. Their size is now Tubvz f ** inch, 

 aud they finally attain a length of g "A f 

 an inch." These long vibrios are gradually 

 changed into cells, which Dr. Calvert calls 

 mierozyms, the first step in transformation 

 being their division into two independent 

 bodies. An extremely faint line appears 

 across the animalcule's centre, increasing in 

 distinctness until the vibrio looks like two 

 individuals joined together. Then they 

 separate, acquiring each an independent 

 existence. The parts again divide and sub- 

 divide, until they appear to be no more 

 than cells endowed with great natatory 

 power. In twelve months or so the vibrios 

 disappear, being succeeded by mierozyms, 

 either in motion or at rest. If these latter 

 be placed in a solution of fresh albumen, 

 vibrios are abundantly developed, appar- 

 ently because they have now all the circum- 

 stances favorable to 

 production. 



their growth and re- 



Exp crimen ts on tlis Circulation of the 



Frog. Certain drugs, such as digitalis, 

 veratrum, and ergot, when taken into the 

 system, are known to exert a powerful influ- 

 ence on the apparatus of circulation, and, 

 on this account, are largely employed by 

 physicians as medicinal agents. In order to 

 learn something further of the manner in 

 which they act, Dr. Boldt has been studying 

 the effects produced by their active princi- 

 ples when thrown into the circulation of the 

 frog. Curarized frogs had the intestines and 

 mesentery exposed, so that the movement 

 of the blood in these parts could be readily 

 watched through the microscope. Twelve 

 experiments with digitalin, injected hypo- 

 dermically, showed that it produces a strong 

 contraction of the peripheral vessels, which 

 is followed by a marked slowing of the 

 pulse, and this, if the dose be large enough, 

 by laming of the heart, as shown by small- 

 ness, irregularity, and rapidity of the pulse, 

 with a vibrating or undulating blood- 

 stream; finally, after a short increase in 

 rapidity, the pulse falls with great sud- 

 denness, and then, with general vaso-mo- 

 tor paralysis, the animal dies. Eleven ex- 

 periments with veratrin showed that it 

 directly paralyzes heart and arterial mus- 

 cles, there being an immediate lowering of 

 the pulse-frequency, the size and force of 



its wave, and an increase in the lumen of 

 the vessels. Twelve experiments with er- 

 gotin resulted in a constant lowering of the 

 pulse-rapidity, by both large and small 

 doses, accompanied by peristaltic or wave- 

 like contractions and expansions of the ar- 

 tery. 



Paper Car-Wheels. Car-wheels of pa- 

 per, though universally admitted to be su- 

 perior to those of iron or steel, have not 

 been much used hitherto, owing to their 

 high price. If, however, as is claimed, pa- 

 per wheels are more durable than those of 

 other materials, and if they do less injury 

 to the tracks, besides being safer and more 

 noiseless, it may in the end be found eco- 

 nomical to employ them. The Connecticut 

 River Railroad, as we learn from the Iron 

 Age, is about to give these wheels a practi- 

 cal trial, having ordered a set of them for 

 the forward truck of a locomotive. The 

 process of manufacturing wheels of paper 

 is as follows : A number of sheets of com- 

 mon straw-paper are compacted together 

 under a pressure of 350 tons. The mass is 

 then turned perfectly round, and the hub 

 forced into a hole in the centre. The tire, 

 which is of steel, has a bevel of one-quarter 

 of an inch on the inside edge, and the pa- 

 per filling is forced in under a pressure of 

 250 tons. Two iron disks, one on either 

 side, and bolted together, keep the filling 

 from coming out ; but, as the tire bears on 

 the paper and not on the disks, the wheel 

 partakes of the elasticity of the former. 



Bicla's Comet. Arago, to quiet all ap- 

 prehensions of a collision of the earth with 

 Biela's comet, made an accurate calculation 

 of its orbit and periods, and so showed that 

 such a catastrophe could not occur for 

 thousands or even millions of years. But, 

 as Prof. Daniel Kirk wood shows, in the 

 Journal of the Franklin Institute, the break- 

 up of that comet, which was observed in 

 January, 1846, very materially alters the 

 conditions of the problem, and now Prof. 

 Kirkwood announces the latter end of No- 

 vember, 1892, as the time when, in all prob- 

 ability the earth and the comet will come in 

 collision. The comet's period is about six 

 years and eight months. After the break- 

 up of January, 1846, it reappearance in 



