Aug. 6, 1874] 



NA TURE 



261 



smaller vessels in a wonderful condition of purity, if care 

 be taken to remove dying specimens and if no feeding be 

 going on. Development of eggs and larvre may be studied 

 without the necessity of changing the sea-water excepting 

 at considerable intervals of time, and marine animals of 

 the most varied types can be kept alive very long indeed 

 at a very small expenditure. 



If put into practice by any private zoologist or laboratory 

 in Britain, the results will most probably be no less grati- 

 fying than they have been in the above-named places 

 where the system has only as yet been carried out. 



A little more costly but still more efficient is a 

 zinc gasometer, which can contain about half a million 

 cubic centimetres of air, with a diameter of about 60 

 centims. This may be placed as it is in Erlangen with- 

 out difficulty in the corner of any laboratory. It is wound 

 up every morning by means of a simple capstan, and the 

 pressure is effected by stones put on the top. The quan- 

 tity of air escaping can be accurately regulated by her- 

 metic taps in the conducting tube. 



The great advantage which it has in common with the 

 apparatus described above is that it remains active with- 

 out further interference for a space of twenty-four hours. 



FOSTER'S "PHYSIOLOGY" 



Physiology. (Science Primers). By M. Foster, M.A., 

 M.D., F.R.S. (Macmillan and Co., 1874.) 



IT is extremely seldom that a fairly informed reader 

 can lay down any text-book, after having read it 

 from end to end, and feel that it has completely fulfilled 

 the purpose for which it was written. Either the method of 

 explanation is imperfect and involved, the facts that are 

 given being correctly stated, or the language may be 

 excellent at the same time that there is a want of 

 attention to accuracy. We believe, however, that all 

 will agree with us in thinking that in this short " Science 

 Primer " Dr. Michael Foster has succeeded in producing 

 an introductory manual which is perfect in itself, and 

 quite a type for future authors of similar productions. 



Manv who devote themselves to the higher branches of 

 scientific inquiry seem to have an inborn fear of putting 

 the arguments and facts of their favourite subject in any 

 but the most uninteresting and uninteUigible language. 

 They write on the assumption that their readers are all 

 as well informed, or nearly so, as themselves on the litera- 

 ture of the science of which tliey treat ; consequently, to 

 the majority their works are of comparatively little value. 

 This imperfection is manifest in many text-books, the 

 utility of which is thereby reduced below that of many 

 otherwise less worthy productions to the co.-nmencing 

 student. 



In the work before us, however, we think that Dr. 

 Foster has succeeded, beyond any author with which we 

 are acquainted, in placing himself on a level with his 

 intended readers, and in putting the fundamental prin- 

 ciples of physiology before the commencing student in a 

 language, and by means of a consecutive argument, 

 which possesses quite sufficient intrinsic attraction to 

 tempt anyone with the least predilection in that dfi-ection, 

 to study, reason out, and attempt to verify his statements. 

 Dr. Foster's similes are peculiarly to the point, and are 

 at the same time drawn from such well-known sources, 



that no one will have the least difficulty in perceiving their 

 applicability, at the same time that he will be able to 

 realise the full importance of their bearing. The follow- 

 ing is one of the best of these, and will well repay the 

 reading . — 



" When you look down upon a great city from a high 

 place, as upon London from St. Paul's, you see stretched 

 below you a network of streets, the meshes of which are 

 filled with blocks of houses. You can watch the crowds 

 of men and carts jostling through the streets, but the 

 work within the houses is hidden from your view. Yet 

 you know that, busy as seems the street, the turmoil and 

 press which you see there are but tokens of the real 

 business which is being carried on in the house. So it is 

 with any piece of the body upon which you look through 

 the microscope. You can watch the red blood jostling 

 through the network of capillary streets. But each 

 mesh bounded by red lines is filled with living flesh, 

 is a block of tiny houses, built of muscle, or of skin, or of 

 brain, as the case may be. You cannot see much going 

 on there, however strong your microscope ; yet that is 

 where the chief work goes on. In the city the raw 

 material is carried through the street to the factory, and 

 the manufactured article may be brought out again into 

 the street, but the din of the labour is within the factory 

 gates. In the body the blood within the capillary is a 

 stream of raw material about to be made muscle, or bone, 

 or brain, and of stuft" which, having been muscle, or bone, 

 or brain, is no longer of any use, and is on its way to be 

 cast out. The actual making of muscle, or of bone, or of 

 brain, is carried on, and the work of each is done, outside 

 the blood, in the little plots of tissue into which no red 

 corpuscle comes." 



Notwithstanding the simplification of the argument to 

 its extreme degree, no attempt is made to arrive at this 

 simplification at the expense of truth. We are not in- 

 formed, as is often said, that venous blood contains car- 

 bonic anhydride dissolved in it, whilst in arterial blood 

 this is replaced by oxygen ; but more accurately, though 

 less simply, that " both contain, dissolved in them, 

 oxygen, nitrogen, and carbonic acid ; venous blood con- 

 tains less oxygen and more carbonic acid than arterial 

 blood." 



Some will think that many of the straightforward facts 

 of the circulation should not be studied until they 

 can be appreciated, unassisted, in their logical sequence ; 

 but we think that the following quotation will give a 

 reality to the peregrinations of a blood-corpuscle which 

 comes home to even very young minds. "Suppose you were 

 a little red corpuscle, all by yourself, in the quite empty 

 blood-vessels of a dead body, squeezed in the narrow 

 pathway of a capillary, say of the biceps muscle of the 

 arm, able to walk about, and anxious to explore the 

 country in which you found yourself. There would be 

 two ways in which you might go. Let us first imagine 

 that you set out in the way which we will call backwards. 

 Squeezing your way along the narrow passage of the 

 capillary in which you had hardly room to move, you would 

 at every few steps pass, on your right hand and on your 

 left, the openings into other capillary channels as small 

 as the one in which you w-ere. Passing by these you 

 would presently find the passage widening, you would 

 have more room to move, and the more openings you 



