once again becomes mentally disabled and awaits his probable death, just as has happened to Algernon.

Your question brings up the issue of what animals are capable of experiencing both intellectually and emotionally. The poignancy of Charlie's story lies in his awareness of what is happening to him as the process reverses itself and he realizes he'll become what he once was, a man who is (in the parlance of that time) mentally retarded. From the standpoint of emotion and self-awareness, Charlie would have been better off if the experiment had never been carried out and he had never been given a chance to experience life as not only a mentally "normal" person, but a genius as well.

Can a mouse, or any animal, feel the same sense of loss and impending doom that a person feels ? The famous poem "To a Mouse" by Burns reflects our conventional assumption that this is not so, and in Burns's view this is to the mouse's advantage:

For thou art blessed, compared with me,

The present only toucheth thee.

But och ! I backward cast my eye

On prospects drear,

And forward, though I canna see,

I guess and fear !

Yet none of us can know the inner mental experience of an animal. The fact that animals do not possess language, the chief element of communication from the human perspective, has made us assume that they cannot think on any but the most rudimentary level. But how do we know this ? A secondary question relates to Algernon's intelligence having been artificially raised to a level not possible in the natural environment. So the possibility does exist that Algernon has been able to feel the same level of loss, regret, and terror of both the reversion to his former self and his impending death, just as Charlie tragically does.

In the short story "Flowers for Algernon," Charlie Gordon, like the mouse Algernon, receives an operation to improve his intelligence. They are both the first of their kinds to go through this process. Also like Algernon, it takes a while for Charlie to become more intelligent. Algernon becomes a super mouse, able to navigate mazes that no other mouse could, and Charlie's intelligence and knowledge skyrocket to genius levels. For example, he knows Hindustani and Chinese and understands the mathematical variance equivalent in Dobermann's Fifth Concerto. 

However, over time, Algernon becomes uncooperative and no longer wants to run the mazes. Charlie notes that Algernon is starting to regress mentally, and that his glandular activity has slowed. In addition, he is showing signs of progressive amnesia, meaning he can't form new memories or learn new tasks. Charlie uncovers what he calls the Algernon-Gordon Effect, which states that one's intelligence (after one has gone through the surgery and become smarter) declines as rapidly as it increased. Algernon dies, and the dissection shows his brain had decreased in size. Charlie also begins to suffer from deterioration and can't remember what he learned recently. He becomes slothful and unmotivated, and he can no longer understand the books he once read. He returns to his old janitorial job, and he asks his former teacher to place flowers on Algernon's grave, as Charlie fears his own death is also near. Both man and mouse go through the same process of rapidly increasing their intelligence and then going through a rapid decline, and their lives are sacrificed to science. 

Charlie, a mentally handicapped human, and Algernon, a mouse, are both "lab rats" used for an experiment. They are forced to compete with each to solve mazes meant to test their intelligence.

Charlie identifies with and develops feelings of compassion  for the mouse. However, at first, Charlie dislikes the mouse because it beats him all the time. He also has competitive feelings towards it. Charlie records the following:

 He says it took a long time with Algernon before he got 3 times smarter then he was before. Thats why Algernon beats me all the time because he had that opera· shun too. That makes me feel better. I coud probly do that amazed faster than a reglar mouse. Maybe some day III beat Algernon. Boy that would be something.

As Charlie's intelligence increases and he beats the mouse, he develops compassion and sympathy for the creature.

They let me hold him for a minit. Hes not so bad. Hes soft like a ball of cotton. He blinks and when he opens his eyes their black and pink on the eges. I said can I feed him because I felt bad to beat him.

Charlie's emotions gain more sophistication. Through his feeling that Algernon is being treated poorly, he expresses his sense that his own treatment by the scientists is wrong. He decides he will befriend Algernon.

I dont think its right to make you pass a test to eat. How woud Dr Nemur like it to have to pass a test every time he wants to eat. I think I'II be frends with Algernon.

Because of his identification with Algernon, Charlie can see ahead of time what his own deterioration will be like. Algernon bites him one day and Charlie records the following:

He was unusually disturbed and vicious.

When Algernon dies, Charlie mourns for the mouse, who was so much like him.

I put Algernon's body in a cheese box and buried him in the back yard. I cried.

Through his unfolding relationship with the mouse, we track Charlie's growth in both intellectual and moral awareness and his sad decline. We understand more clearly, too, the way Charlie has been used as nothing more than a lab animal.