228 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1918. 



most part, are merely held within a tangle of threads. In the sphag- 

 num we find a highly specialized absorbing system, made up pri j 

 marily of a vast series of absorbing cells, but supplemented to a 

 high degree by various other structural peculiarities of the sphag- 

 num plant. 



SURGICAL AND NON-SURGICAL SPECIES OF SPHAGNUM. 



By no means all species of sphagnum are of equal value for use in 

 surgical dressings. Failure to appreciate this fact, and the indis- 

 criminate use of any and all species of sphagnum, without doubt, was 

 responsible for much of the dissatisfaction with sphagnum dressings 

 which was expressed by many surgeons in the early days of the 

 sphagnum enterprise. Some species of sphagnum (pi. 1), indeed, 

 are practically useless for this purpose and by far the larger number 

 are of little value. On the continent of North America there are at 

 least 40 different species of sphagnum; in the little State of Con- 

 necticut alone there are no less than 25 ; and of all these there arc only 

 4 that have actually been used to any extent in making surgical 

 dressings. It is not enough, then, to be able to recognize sphagnum 

 as sphagnum. One must be able to differentiate between suitable 

 and unsuitable varieties. 



Now, from a botanical point of view, the sphagnums are an ex- 

 ceedingly difficult group of plants to deal with. The accurate de- 

 termination of specimens is work for an expert. Fortunately, how- 

 ever, the recognition of material suitable or otherwise for surgical 

 jmrposes is not especially difficult, since all four of the species 

 which are most highly recommended belong to one well-marked sec- 

 tion of the genus, the so-called " Cymbifoliunh " group. With a lit- 

 tle training and experience it is well within the ability of almost 

 anyone to at least distinguish with some degree of certainty between 

 sphagnum which very likely will prove of surgical value and 

 sphagnum which quite certainly will not. 



Without going too much into detail, then, we will consider next 

 just what qualities are desirable in sphagnum material which is to be 

 used in surgical dressings. 



First of all, the highest possible capacity for absorbing liquids is 

 essential; and with reference to this qualification there is a wide 

 range of variation between different species. In general, the more 

 robust varieties of sphagnum are better than the more delicate; 

 forms with large leaves, dense foliage, and close-set branches are 

 much better than varieties with small leaves, skimpy foliage, and 

 scattered branches. In the second place, it is essential that the ma- 

 terial should be soft and flexible, and at the same time that it should 

 possess a considerable degree of tensile strength. Here, again, there 

 is great variation between different species. In general, coarse or 



