HARD WICKE'S SCIENCE- G OSS IE. 



251 



represented by a uniform transparent mass in which 

 the microscopist finds nothing to study, and in all 

 the smaller kinds of insects they are also in a more 

 or less transparent condition containing more or less 

 opaque masses, covered with a well-preserved integu- 

 ment and to this state they are reduced by the 

 preserver. 



"In England we sometimes find preparations that 

 are mounted without pressure ; in these the insect is 

 placed in the middle of a thick mass of balsam 

 after having been impregnated with some essential 

 oil to render them transparent, and not being pressed 

 they are not deformed. 



" Some of these preparations are very successful, 

 particularly those of spiders ; we can also perceive 

 the remains of the internal organs, the muscular 

 system, for example. I have also made a good many 

 of them, but although they possess some advantages, 

 their thickness (sometimes several millimetres) prevents 

 their being studied with objectives of a short focus. 



' ' I would not say that all preparations which I call 

 trivial are useless : most certainly not. If they are 

 not satisfactory to savants, they interest amateurs, 

 and they teach many things that otherwise would 

 not have been known. They are also useful in 

 England, where they are sold in large numbers, 

 because among our neighbours the microscope is 

 more used for amusement and as an object of luxury 

 than for working purposes. 



"The young 'misses' in the drawing-room are 

 better amused with, and, I believe, more usefully em- 

 ployed, in admiring the delicate little comb that forms 

 the claw of a spider's foot, or the elegant little scales 

 that enamel the wing of a butterfly, than in examining 

 the insipid portraits in a keepsake. 



"These slides, that for us have little interest, are 

 therefore in this point of view of real utility. They 

 give to ordinary people the taste for natural objects, 

 and they furnish a thousand little instructions acquired 

 ■without labour, and are also amusing. We must, 

 therefore, not too much despise them. 



"How is it that preparations of diatoms are 

 always satisfactory? Primarily, because they are 

 in reality the most easy to make. The diatoms 

 relatively require but little manipulation to prepare 

 them for mounting, and in consequence of their 

 beauty the study of these little organisms has largely 

 increased. The preparers are, therefore, all more or 

 less, diatomists ; they know what to do, they know 

 how the object ought to be mounted. Certain vege- 

 table organs are also well displayed, as there the 

 preparer also knows how best to mount them as 

 trachea, stomata, ovules, spores, organs of fructifica- 

 tion, &c. But when they attempt animal anatomy, 

 whether that of the vertebrates or invertebrates, 

 whether normal or pathological histology, the pre- 

 parers, with very rare exceptions, have not sufficient 

 knowledge to know what is necessary to make visible, 

 what is the characteristic detail he should render 



evident in order to make the preparation instructive. 

 They imagine it to be sufficient to take a piece of 

 tissue, injected or otherwise, harden it, make longi- 

 tudinal and transverse sections, then steep it in 

 carmine, mount it in a beautiful cell, and by these 

 means obtain a slide useful for something. This is 

 a grave error. For example, I have before me 

 various "commercial" histological preparations, 

 disassociated muscular fibre, a torn nerve filament, 

 a slice of conjunctive tissue, the nerve terminations 

 on a muscular fibre. What do I learn ? The muscular 

 fibres have not been stretched. I do not see sarco- 

 lemna made evident, nor the nodes, nor the least 

 detail of the strice, discs, and transparent spaces. 



"The nerve filament shows me some little clotted 

 threads scattered in the midst of a small cloud of 

 conjunctive tissue, but of the myaline sheath, the 

 cylindrical axis, the annular constrictions of the 

 nodule of the segments of the endothelial cells (I do 

 not speak of sections) I see nothing of all these. 



" In the connective tissue I look in vain for a distinct 

 element, the connecting fascia, and the elastic fibres, 

 all is confusion, and the conjunctive cells are absent. 

 In the nerve terminations on muscular fibre, I see a 

 small yellow patch on the fibre ; this is the motor 

 plate, but the sheath, the ramifications, the nodules 

 of various kinds, are all invisible. 



" You will tell me that of all specimens, histological 

 are the most difficult and tedious to prepare, and that 

 it is generally impossible to show all these details 

 in one preparation. This is true, but it is only a 

 secondary reason. These difficulties are overcome 

 by the facility given by practice. 



" If one wishes to see all the details of structure in 

 any particular organ, it is necessary to make many 

 preparations. Alas ! as I before remarked, preparers, 

 with very few exceptions, have not sufficient histo- 

 logical knowledge, and are ignorant of the necessary 

 technical methods, or even the will, because they 

 are tedious and delicate, and they moreover fear that 

 the increased cost of these preparations would frighten 

 those who might wish to acquire them. I believe there 

 is no foundation for this last reason, and I judge from 

 the daily demands for preparations made on these 

 principles, even at an increased cost, when they are 

 really instructive, and I cannot doubt it when I see 

 the most common specimens of Pedicultis pubis, sold 

 in America for 5 fr. 75 c, in which country it is not 

 rarer than in France." 



Echium vqlgare is not so uncommon in our 

 neighbourhood as your correspondent T. Comlidge 

 supposes. It grows in large masses on the beach 

 between Portslade and Cliftonville, on the road from 

 Bramber to Shoreham, and many other spots, but it 

 does not generally make its appearance on the Downs, 

 except in basin-shaped holes, where it sometimes 

 attains considerable dimensions. — Benjamin Lomax. 



