Whether the yew be poisonous—no unimportant matter, as will shortly be seen—has been discussed frequently and at great length. The disputants often argue at cross-purposes, each side in turn misapprehending the exact point at issue. Having read all the literature which is reasonably accessible on this subject, I am convinced of the overwhelming proof that the yew has poisonous properties, though the noxiousness may be comparatively slight at certain seasons, in certain years, and with respect to certain animals. The results are most fatal when the beasts eat the leaves on a fasting stomach. When the leaves are dry and tough there is the additional evil of indigestibility. Yet there is an opposing fact. Mixed with three or four times their bulk of other food, green yew leaves are actually employed as fodder for cattle in times of scarcity. Records of this custom come from Hanover, Hesse, and other parts of the Continent. Stated in general terms, then, the poisonous principle (taxine) cannot be very intensely concentrated; it may even be inoperative until acted upon by the juices of the stomach. Again, the pulpy portion of the fruit is eaten with impunity, but the stones are considered highly injurious. Sufficient references are given in the footnote to obviate further discussion here[939], but it will be seen later that the modern theory was preceded by an empirical knowledge which harmonizes well with the ascertained facts.
The belief in the pernicious properties of the juice of the yew is, indeed, as old as Pliny, who tells us that arrows were dipped in the poison (toxicum), and that the hurtfulness might be neutralized by previously driving a brass nail into the tree[940]. He adds that some writers have asserted that toxicum was formerly taxicum, from the name of the yew (taxus). The assumption seems to be that taxus is connected not only with τάξος, a yew, but also with τόξον, a bow (τὰ τόξα = bow and arrows, and perhaps arrows only)[941], and φάρμακον, poison. But even if these links be allowed, the claim is vitiated by the refusal of the lexicographers to admit such a word as taxicum.
Caesar informs us that Cativolcus, one of the rulers of the Eburones, poisoned himself with yew[942]. Since a doubt has been raised whether the Latin taxus and the Greek τάξος accurately represent our word “yew,” it may be said that the latest authorities on both languages give that rendering to the respective words[943]. It must nevertheless be observed that there is an alternative word in Greek, for one of the several meanings of σμῖλαξ, or μιλαξ, is “yew.” Pliny’s word tristis (sad), applied to taxus, stands good therefore for the yew. It has been suggested that the Greek word is allied to τάξις, arrangement (from τάςςω = I arrange), the allusion being to the apparent double row of leaves.
Before leaving the philological section, some English equivalents of the word must be noticed. “Early Modern English” forms include yewe, yeugh, eugh, yowe, etc. These come to us from the Middle English ew or u, and these, again, represent the A.S. īw and eów[944]. A seventh century manuscript has a still earlier form, īuu, and this is said to be the oldest spelling in any Teutonic language[945]. There are, says the Century Dictionary, Danish, Old High German, Spanish, Old Irish, Welsh, Gaelic, and Cornish equivalents, and of these, the Celtic forms are possibly original and not derivative[946]. Professor W. W. Skeat supports the Celtic origin of the word yew, which, by the way, is quite distinct from the word ivy, although the various forms of yew and ivy suggest one another[947]. Dr Schrader says that the Old High German word iva, in the sense of “yew,” disappears as we go further East, and, in Sclavonic dialects, signifies a willow. The same holds good of the word for “beech,” and Dr Schrader believes that the change is due to the thinning out of these trees Eastwards. In Lithuania, again, the meanings of “fir” and “yew” run into each other[948]. Professor V. Hehn called attention to the same series of facts, from which he drew similar conclusions.
The etymological road leading us no further, we take counsel of the forester and the arboriculturist. We wish to ascertain the greatest age which the yew is believed to reach.
The older authorities followed implicitly the dictum of the Swiss botanist Augustin De Candolle, who, basing his conclusions upon a study of the annual rings of the yew, and upon the sizes of yews of known age, formulated the rule: An increase in diameter of one line annually. If we allow an average yearly growth of one line in diameter, we shall probably over-estimate the rate of growth for very aged trees (“il est probable qu’on est au-dessus de la vérité”), so that while we may, in practice, reckon each line of the diameter as a year, we shall, in reality, make the trees younger than they actually are[949]. De Candolle, in another place, admitted that for the first 150 years the annual growth somewhat exceeded a line in diameter, though for older trees it was less than this amount[950]. Abridging this rather involved statement, let us put the rule thus: Up to the age of 150 years the yews increase annually a line or a little more in diameter, and a little less than a line afterwards.
Since De Candolle’s day, it has been contended that his estimate makes the trees too old. Dr J. Lowe, in his interesting volume on Yew-Trees, has combated the conclusions at some length; his chapters are here freely drawn upon and compared with my own private notes. Dr Lowe’s estimate, taking young and old trees together, allows a growth of one foot in diameter for each period of 60-70 years. De Candolle’s rule would make a like growth represent 144 years at least (1 foot = 144 lines), or, supposing him to have taken the line as one-tenth of an inch—as some writers mistakenly believe[951]—120 years, or a little over. In the absence of testimony to the contrary, I think we may safely consider that De Candolle’s line was reckoned on the one-twelfth basis: indeed there appears to be no valid reason for doubting this. We note, in passing, that the calculations of Edward Jesse, the naturalist, made after measuring trees at intervals, agree closely with those of the Swiss savant[952].
Between the estimates of De Candolle and those of Dr Lowe, but far nearer to those of the latter observer, is the determination adopted by Sir R. Christison and his son, Dr D. Christison. Working on the eminently scientific method of measuring the increase of girth at a fixed point during stated periods, these observers decided that one foot for every 75 years would be more than the average rate of increase[953]. The three varying results may therefore be thus stated:
| De Candolle | 1 foot represents | 144 years |
| The Christisons | ””” | 75 years |
| Dr Lowe | ””” | 60-70, say 65 years |
Mr J. E. Bowman, making use of the trephine, came to the conclusion that young trees may add two lines per year, and if the soil be very rich, three lines, but that, after a diameter of two feet has been reached, De Candolle’s limit of one line yearly holds true. De Candolle’s formula, Bowman considered, “makes old trees too young, and young trees too old.” Commenting on Bowman’s mode of experiment, Dr Lowe asserts that it has “no utility whatever,” because the external rings of the tree—those reached by the trephine—are not concentric, and are not formed in the same manner as those of the young shoot. Further, Bowman’s experiments seem to have been performed on young trees only[954].