砂質土에서 孵化發育이 甚히 良好하나 死滅 또한 速한 것은 表土가 容易히 乾燥하는 까닭임이 實驗的으로 證明되엇으며, 이는 晴雨가 反復되는 砂質土住民이 低感染狀態에 있음은, 表土의 關係에 있을 것으로 推測한 Beavor의 所論을 立證하는 것이다.
以上의 實驗을 通하여 人工組成土壤內의 成績이 自然土壤內에서의 그것과 一致符合됨을 보았으며, 이는 自然土壤을 土台로 하는 各 實驗成績의 價値를 判定하는 데 基本材料를 提供하는 것으로 믿는다.
第3. 土壤內 十二指腸蟲幼蟲에 對한 各種基肥의 影響
人糞施肥로 汚染된 土壤에 榮農上 各種肥料의 撤布가 感染幼蟲生存에 어떠한 役割을 하는지 그 間의 消息을 究明함은 重要한 問題다. 이 方面의 硏究에 對해서는 거의 放置된 感이 不無하며, 다만 石灰窒素의 分解課程에서 遊離 發生하는 Calcium Cyanamide, Cyanamide의 毒性作俑에 着眼하여 實施한 實驗 및 數三化學肥料로서의 實驗報告를 볼 뿐이요, 餘他의 化學肥料 및 民間自家製造肥料로서의 實驗은 없다.
本實驗에서는 짚재, 톱밥, 堆肥 等 在來民間肥料와 酸安門, 過燐酸石灰, 生石灰, 化加里, 銷石, 石灰窒素 및 尿素 等 10種 肥料를 擇하여 각 0.3%의 比率로 自然 砂壤土와 混合後 感染幼蟲을 撤布하여 其成績을 觀察한 바 다음의 結論을 얻었다.
1. 石灰窒素混合土壤內에서는 大多數幼蟲이 12-24時間 以內에, 48時間內에는 그 全部가 死滅한다.
2. 짚재, 톱밥, 堆肥等 在來肥料는 何等의 殺蟲力이 없다. 石灰窒素 以外의 肥料, 特히 짚재, 톱밥은 民間에서 殺蟲力이 있는 것으로 믿어 왔으나 根據가 없음이 明白하다.
第4. 都市 및 農村地帶土壤의 十二指腸蟲卵 및 幼蟲의 汚染狀態
經皮感染이 汚染土壤에서 由來한다 함은 周知의 事實이다. 土壤汚染調査는 疫學的見地 에서 極히 重要視되는 問題다. 이러한 調査文獻은 諸外國에 있어서는 흔히 볼 수 있으나, 韓國에 있어서는 日政時 서울 市內에서 數個處의 土壤을 調査한 바 있으나 農村地帶에서의 調査는 아직 그 例가 없다.
2. 芥子(1gm/dl)와 마늘(20gm/dl) 汁에서는 被束幼蟲의 抵抗力ld 가장 弱하여 24時間以內에 死滅한다.
3. 芥子와 마늘을 加熱하면 殺蟲作用이 顯著히 低下한다.
4. 김치의 作用은 蟲卵과 幼蟲의 抵抗力에 別影響이 없다.
[영문]
It has been frequently proved that hookworm infection mostly comes through skin and rarely through mouth. The incidence of hookworm infection among the people of Korea has increased in recent years and so represents and alarming public health problem in Korea.
The custom of using human excretions as fertilizer, barefoot life throughout the farming seasons, the custom of eating Kimchi (a common and an important kind of food in daily use.), favorable condition of climate and moisture. These are all major factors in the development of hookworm disease in this country.
It might be supposed that different food habits, customs, living environment and farming systems in various nations would produce a different method of infection. Koreans, for the most part do not know as to how their peculiar customs affect the spread of this disease.
In this investigation, an attempt was made to clear up the routes of infection according to the customs and food habits, and some basic point in regard to the modes of infection.
In the first part of this study, the experiment was undertaken to compare the modes of infection, or to describe the distribution and persistence of the larvae of Ancylostoma coninum, A. duodenale and Necator americanus in relation to
different methods of inoculation in the mouse.
The results proved that there was a considerable variation in the yields at different times and from different tissues. The results in general, however, were essentially the same regardless of the mode of inoculation.
In the second part, because all former experiments on the development of hookworm larvae were made with natural soil, in the present experiment it was decided to use six different kinds of soil. Sand, sandy soil, silt, silt soil, clay and clay soil were used following the descriptions of the U.S. soil texture, to demonstrate moro clearly the differences of natural soil composition.
The results revealed that the degree of water absorption was determined by the sand content and, on the other hand, the ability to retain water was determined by the content of clay in the soil. When mixed with soil under saturated water conditions, the development of larvae were favorable in sandy and silty soil ; whereas they showed poor development in the sand and clay. A good development also occured when eggs were applied on the top of the soil. Regarding the amount of moisture required, the hatching of eggs was excellent under half saturated soil conditions. The fact that the larvae disappeared rapidly in the sandy soil, despite good development of eggs, would be due to the top soil drying up quickly.
The results obtained from this study, lead to a clear conclusion that the development of larvae depends upon both the type of soil and its moisture content.
In the third part, the experiment was made on the fate of filari-form larvae in soil mixed with various chemical fertilizers (7 kinds) and several domestic manures (3 kinds), and it was proved that there was no wormicidal effects in any of the
chemical or domestic manures, except in calcium nitrate when it mixed in the concentration of 0.3% in the soil.
In the fourth part, the soil survey was carried out to examine the degree of contamination with hookworm eggs and larvae in the soil of different areas of Seoul city and around a rural village.
The damp roadside soils obtained from unsanitary districts of Seoul contained hookworm eggs. Heavy contaminations of infective stage larvae (9. -27.3%) were found from soil polluted with contaminated night-soil, roadside soil, and soil around public latrine and manure heap sheds in the rural area.
The soil contamination with hookworm in Seoul and rural areas reveals the existence of fecal matter in the soil which may have been caused by direct pollution through fertilizing or carried by man and domestic animals, as well as by physical agencies, such as rain and streams, providing larvae to infect man via the cutaneous route.
In the fifth part played by the survey was carried out on market vegetables to examine the contamination with filariform larvae, and some points in the existence of larval migration in relation to the dew fall and rain ; an examination on parts of vegetables, such as loaves and roots as a site for larval migration ; and finally the number of times to wash vegetables for the purpose of removing all larvae.
It was found that around 11.1% of the market vegetables were contaminated with filariform larvae. The experiments on larval migration on leaves was confirmed to coincide with the fall of dew and rains. The migration seemed to concentrate more on the part of the leaf attached to the root rather than on other parts of root. On washing vegetables, more than three repeated washing would be necessary to remove all larvae.
In the sixth part, the experiment was carried out on Kimchi (Pickle) and its ingredients, mixing hookworm eggs, larvae into Kimchi juice to examine its resistant ability. The Kimchi was made 17 different ways in both Korean and western style, and 13 different elements of Kimchi preparations were selected for the
experiment.
All eggs had disappeared within 3 days in all kinds of Kimchi, the rhabditoid larvae were all dead within 5 minutes in the solutions of Kimchi, and filariform larvae completly disappeared in all kinds of Kimchi within 48 hours.
Out of 13 substances, garlic and mustard solutions had a remarkable wormicidal effect on eggs and larvae. On the other hand, remarkable weakening of the wormcidal action resulted when both elements were boiled 30 minutes at 100℃. No significant effect on eggs and larvae was shown by the fermentation of the ripening Kimchi.