August 1, 1895.] 



KNOWLEDGE. 



175 



confirmation. These insects are allured by the glands on 

 the stem and leaf to the margin of the pitcher, proceeding 

 by way of the under surface of the winged petiole, on 

 whose ridge are numerous nectar-secreting glands. The 

 wings also sliield them from the rays of the sun and from 

 the observation of foes. Having reached the pitcher rim 

 they strive to obtain nectar from the orifices of the 

 marginal glands, and in their eagerness they over-reach 

 themselves and fall into the cavity of the pitcher, from 

 which escape is practically impossible. 



In connection with the visits of ants to Nepenthes, an 

 extremely interesting circumstance has been noted which 

 seems to throw some light on the doctrine of acquired 

 characters — a point of dispute amongst biologists. 

 Nepenthes bicakarala is infested by a particular species 

 of ant. On the tendril opposite the bottom of the pitcher 

 is a small swelling. In specimens obtained from its native 

 habitat a round hole has, as a rule, been drilled in the 

 swollen portion ; but in those grown in our conservatories, 

 although the swelling is always present, it is never 

 punctured. The suggestion has been made that the ants, 

 finding it impossible to obtain the liquid contents of the 

 pitcher in the ordinary way without fatal issue to them- 

 selves, have resorted to this method from an instinctive 

 knowledge of the fact that water will rise to its own level, 

 for when the swelling is punctured the liquid in the pitcher 

 oozes from cell to cell until it reaches the aperture. The 

 extra supply of liquid thus brought to this region of the 

 tendril causes an excessive growth of the tissues at this 

 point. Owing to the visits of these ants, this hyper- 

 trophy has occurred in the majority of individuals of the 

 species for numberless successive generations, and has so 

 affected the constitution of the plant that now the swelling 

 always appears, although the original inducing cause be 

 absent. 



In the accompanying plate a specimen of the Australian 

 Pitcher plant f Cephnlotus folUcidaris j is shown. It is only 



found in the 

 moorlands of 

 Albany, in 

 Western 

 Au s tral ia. 

 Two idnd of 

 leaves are 

 found on the 

 plant. The 

 laminsEof the 

 lower rosette 

 of leaves are 

 transformed 

 into pitchers 

 to entrap un- 

 wary insects. 

 The pitchers 

 are rendered 

 attractive by their bright colour, and their outer sur- 

 face is provided with nectar-secreting glands. As the 

 pitchers rest on the ground, wingless insects are thus 

 allured into their cavities. Once inside, escape is almost 

 impossible, as a consideration of the structure of the 

 interior of a pitcher will render evident. On the inner 

 edge of the involute margin is a fringe of decurved spines, 

 and every cell of the epidermis below is projected into a 

 sharp downward-directed hair. The rim of the deep 

 circular involution is likewise armed. Then the basal 

 portion of the pitcher is filled with a liquid, into which are 

 exuded an acid and a ferment by glands situated on that 

 portion of the epidermis. 



The trypsin secreted by the pancreas has its analogue in 



FlO. 4. — A. Portiou of epidermis from eou- 

 dueting surface of pitcher of jS'epenthes. Notice 

 the U^nticular cxcreseences (st.J. Tliese are 

 modified stomata. 



the plant kingdom in a ferment found in a tropical plant 

 called the Papan (do-ica papaijo). Green states that the 

 natives of India have for long used the fruit of this plant 

 for cooking with tough meat to make it tender, and that 

 there is a prevalent notion that wrapping its leaves around 

 it, or even hanging it under the tree, has a similar effect ! 

 Certain it is that a ferment — papilin — has been isolated 

 from the fruits, which has the power of digesting various 

 proteid substances. 



The power of the walla of the true stomach of the 

 sucking calf — rennet — to coagulate milk by the secretion 

 of a ferment is famihar to all ; but some plants have a 

 similar property. The common Bedstraw [Galium venim) 

 is even now used by West of England dairymen for this 

 purpose, and in the days of Linnseus the Laplanders put 

 the leaves of Pinfjuicida vuhjaris (the Butterwort) to the 

 same use. Both plants contain a milk-curdling ferment, 

 which has also been found in the stem, leaves, and seeds 

 of various other plants. 



In Piicinus communis (the Castor-Oil plant) the endosperm 

 is oily. If a glycerine extract of the germinating seed be 

 mixed with an emulsion of castor-oil, and kept at a tem- 

 perature of 40° C, the liquid becomes acid, and after some 

 days glycerine make its appearance. If the extract be 

 boiled before it is added to the oil, these changes do not 

 occur. They are the result of the action of a ferment 

 present in the endosperm of the germinating seed. This 

 ferment is thus similar in its action to the steapsin of the 

 pancreas. 



ANTIVENINE. 



By Dr. J. G. McPherson, F.R.S.E. 



IN the July number of Knowledge I communicated 

 some of the results of Prof. Eraser's admirable 

 experiments on snake poisons and their antidote. 

 The other day he laid before the Royal Society of 

 Edinburgh some equally important results. He has 

 continued the same line of experiment with increased 

 success, and he can -now see the very important boon his 

 discovery will confer on the people of India. 



His method is to ascertain the minimum lethal dose for 

 an animal ; to begin experimenting upon a similar animal 

 with a smaller dose. After a short interval he increases 

 this dose, until in time he can inject fifty times the mini- 

 mum lethal dose into the animal's blood without producing 

 any bad effects. This animal is immunized, and its blood 

 serum, injected into another animal of the same size and 

 weight, will prevent the action of snake poison when 

 injected. Besides, if, in an animal which has had snake 

 poison injected into its blood, a quantity of this immunized 

 blood serum be injected within a reasonable time, the 

 poison is antagonized, and is rendered innocuous. This 

 immunized blood serum is called by its discoverer 

 antivenine. 



Prof. Eraser has now found that the blood serum of 

 a rabbit, which had received thirty times the minimum 

 lethal dose, was quite as effective in its antitoxic properties 

 as that of a rabbit which had received fifty times the 

 minimum lethal dose. The latter, however, will survive 

 a much larger dose than the former. Still, for anti- 

 venine purposes,' this is a saving in the very scarce snake 

 poison. 



The most important discovery was to be left for the 

 experiments on the horse. So much poison was required 

 to immunize a horse, that the professor had to defer his 

 experiments until he procured from the Indian Govern- 

 ment a sufficient quantity. This he has secured. In 



