Theory:

4. I went back into the room and sat down on the chair. I opened the box beneath the table and took out a book, the Materia Medica. I opened it at the table on which stood the lamp and a large mirror; a small comb lay beside the mirror.
 
     One feels tempted to look into a mirror when it is near one. I took a look. In those days I was a great admirer of beauty and I believed in making myself look handsome. I was unmarried and I was a doctor. I felt I had to make my presence felt. I picked up the comb and ran it through my hair and adjusted the parting so that it looked straight and neat.
Explanation:
 
The doctor went into his room after spending some time on the veranda. He then sat in a chair and took a book from a box under the table called "Materia Medica." Materia Medica ('medical material/substance') is a Latin phrase used in pharmacy history to describe the body of knowledge about the therapeutic properties of any medicine used for healing. "Homoeopathic Materia Medica" is a record of collection of symptoms of hundreds of medicines. He considered reading the book, but did not do so. There was also a lamp and a huge mirror on the study table, as well as a tiny comb beside the mirror.
 
In general, if a mirror is close to someone, he or she will be tempted to see how they appear at that particular moment. Despite the fact that the doctor was in the mood to read a book, he was enticed to have a look at himself at the time. He looked at him in the mirror. In this narrative, 'mirror' plays a crucial role, which may be understood in the story's concluding portion.
 
The doctor expressed his admiration for beauty to the author and his group. He liked to admire beautiful things as a young man and sought to improve his appearance to look more attractive. Most individuals, especially women, expect to appear beautiful and flawless before getting married. As he was unmarried and a doctor by profession, he felt it necessary to be presentable in front of others. He combed his hair, attempting to adjust the parting, to maintain a neat and good-looking appearance and check how he looked.
 
Meaning of difficult words:
 
S.No
Words
Meaning
1.
Beside
Next to somebody or something
2.
Admirer
A person who likes or respects somebody/something
3.
PartingThe line in a person's hair where it is divided in two with a comb
Reference:
National Council of Educational Research and Training (2006). Beehive. The Snake and the Mirror - Vaikom Muhammad Basheer (pp.56-60). Published at the Publication Division by the Secretary, National Council of Educational Research and Training, Sri Aurobindo Marg, New Delhi.